As Jimmy Heremaia begins a minimum 12-year sentence for the murder of Ariki Rigby, and later arson of the car containing her body, the officer in charge of Operation Sphinx opened up to Neil Reid about the two-year investigation to catch him, including the successful work of two undercover officers.
Ariki Rigby murder: How undercover officers nabbed runaway Mongrel Mob killer Jimmy Heremaia
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It was a sentence stated two years and nine days after the 31-year-old Mongrel Mob member had bludgeoned teen Ariki Rigby to death on a quiet road north of Napier on September 2, 2022.
He then shoved her body in the back of a car, drove it to a park on the outskirts of Havelock North and torched the car.
Ropine Paul – then a Mongrel Mob prospect, but now a fully patched member – helped Heremaia leading up to torching the car. He would later plead guilty to arson.
The tragic chain of events that led to Rigby’s killing began with her being spotted in public wearing a Mongrel Mob T-shirt belonging to Heremaia; a man she had only known for a couple of weeks.
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Despite emerging as the police’s main suspect within two weeks of 18-year-old Rigby’s brutal death and the disrespect of her remains – Heremaia had remained a free man.
But it wasn’t through a lack of trying from the Operation Sphinx team, headed by Hastings-based Detective Senior Sergeant James Keene.
Heremaia was questioned by the investigation team in Auckland about two weeks after her body had been discovered; having fled north after trying to cover his tracks and working on an alibi to throw police off the scent.
Two years on Heremaia would admit to killing Rigby, who died because of injuries suffered by two hammer blows to the head.
The admission came during a conversation on September 13, 2024, with a man called the “Boss” who Heremaia was introduced to by another man, “Luke”, that he shared the same South Auckland accommodation with.
The murder case’s summary of facts says Heremaia and “Luke” had previously engaged in “work” on behalf of the “Boss”.
But little did Heremaia know that “Luke” and the “Boss” were undercover police officers, and that the secretly taped confession would lead to his arrest four days later.
For Keene and the Operation Sphinx team, the confession followed two years of relentless work under trying circumstances - given the gang links to the case.
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And as Heremaia began his sentence, Keene opened up exclusively to the Herald about the challenges faced getting justice for Rigby, and how the police undercover programme helped crack the case amid a “very difficult environment”.
“Jimmy Heremaia being in Auckland, added another layer of complexion for us, because the majority of the investigation team was based in Hawke’s Bay,” Keene said.
“We reached out and utilised the resources available to the New Zealand Police in order to solve these types of incidents, including the undercover programme.
“Those two officers that were involved . . . it’s a fantastic piece of work by them. I can’t speak highly enough of the dedication and the professionalism shown not just them, by their team, and by the management team.”
Keene can’t divulge all the workings of the undercover duo – most notably “Luke” who knew Heremaia the best – to protect the operational security of the undercover programme.
But the summary of facts prepared for Heremaia’s sentencing on the murder charge, and what the senior Hawke’s Bay officer can say, have provided a unique insight into their work.
The killer was befriended by “Luke” who had moved into the same shared accommodation unit in South Auckland that Heremaia was living in.
“Mr Heremaia and ‘Luke’ engaged in ‘work’ on behalf of ‘Luke’s’ ‘boss’, who was also an undercover police officer,” the summary of facts reveals.
On September 13, 2024, “Luke” took Heremaia with him to Auckland Airport to pick up the “Boss”.
It was during a conversation between the latter two that a confession was made.
He told the “Boss” that Rigby was “on guard” when they met in Napier about 30 minutes before he killed her.
She was fearing for her safety amid the anger her being seen wearing a Mongrel Mob T-shirt had caused. She said she had been “attacked” earlier on, and had a hammer with her for safety. She also told Heremaia she had a knife as well for protection.
Heremaia told the “Boss” the pair had had an argument when they were parked north of Napier. Rigby had swung the hammer at him and he had “blocked it, pretty much grabbed it off her and . . . dong.
“I . . . picked the girl up, she attacked me, so yeah . . . I bashed her, threw her in the back . . . torched the car.”
Heremaia went on to tell the undercover police officer that Mongrel Mob chapter hierarchy had put pressure on him to recover the shirt Rigby had been seen wearing.
Although he had done as asked, he said he had not been believed. His gang boss told him to “take care of it”.
“I took care of it,” he told the “Boss”.
He told the undercover officer that he had thrown the murder weapon into a river and police would never find it because of destruction caused by Cyclone Gabrielle.
The ‘gang code’ breach that ended in an ‘tragic waste of life’
There are many questions Keene has asked himself in the two and a half years since Rigby’s death.
Among those is how anger from within the Mongrel Mob over Rigby being seen in a Mongrel Mob T-shirt spiraled out of control and sparked the events that ended in her murder.
Auckland-based Ariki travelled to Hawke’s Bay in early August 2022, to visit family.
Soon after her arrival she met Heremaia, a patched member of the Mongrel Mob’s Flaxmere-based chapter.
Going by some of her social media posts, Rigby seemed fascinated by the Mongrel Mob.
She loved wearing red, the colour associated with the gang. Her posts – including those referencing rap songs the would-be musician was working on - featured sayings adopted by the gang’s members.
One of the last photos she uploaded online – on August 27, just six days before she was killed - was an image of her posing with patched Mongrel Mob members in Flaxmere.
It was in the early hours of August 31 that a patched Mongrel Mob member spotted the teen wearing Heremaia’s gang T-shirt in public.
The sentencing summary of facts reveals the gang member “confronted her” about wearing it.
“Ms Rigby taunted that person, before running away – still wearing the T-shirt,” the court document read.
“It is well known that only people affiliated with the Mongrel Mob gang are permitted to wear gang-related regalia, clothing or symbols. Allowing anybody else to wear any of these items is regarded, by the gang, as being a serious violation of their rules.
“This is particularly so if the non-gang member wearing the item is a female.”
When Heremaia pleaded guilty to her murder in late February, the Napier High Court was told Rigby’s actions had been against the “gang code”.
The summary of facts added “Ms Rigby being seen wearing the Mongrel Mob T-shirt was the catalyst for the event that followed, and which led to her death”.
Word spread quickly, with Heremaia being instructed by gang hierarchy to recover the shirt.
He did that, by tracking Rigby down mid-morning at a house in Flaxmere.
Mob anger about the shirt led to Heremaia being “de-patched”, with a gang member arriving at his family home in Omahu - on the outskirts of Hastings – to collect his gang patch.
Heremaia was told of the action by text about 4pm on September 2, shortly before he made a quick return trip to Wairoa.
He also exchanged messages with Rigby - in one she said she had just “got attacked” - and the pair met up shortly before 10pm.
Within an hour, Ariki would be dead.
“People will read the summary of facts and think, how does it get to this?,” Keene told the Herald. “And we are of the same opinion.
“It seems it’s an absolute tragic waste of life, over ... [someone] wearing a T-shirt in the wrong place at the wrong time.
“Ultimately, Jimmy Heremaia has to be responsible for his actions . . . involving the death of an 18-year-old girl who’s very much an innocent party in all this.”
Tragic texts: ‘Don’t set me up . . . please I’ve had enough for today’
Given what happened on the night of September 2, some of the last text messages Rigby sent make for chilling reading.
They were sent by a young woman who had been “attacked” earlier in the evening, was clearly worried about her wellbeing and was seeking to get away from the gang.
Before being picked up by Heremaia, she messaged him saying she had been involved in an altercation in Napier.
She asked if “he would like to go to Tauranga with her to get away from Napier and the Hawke’s Bay Mongrel Mob” the summary of facts said.
While the two were communicating, Heremaia got a message from his “Mongrel Mob hierarchy”, the court summary says, telling him: “Find that FLAXMERE tee-shirt dog, get it done”.
Despite already regaining the shirt, he replied: “I am brother”.
Before Rigby was picked up by Heremaia, other messages she sent to him read “Don’t set me up”, “Please I’ve had enough for today” and a third message saying “Otherwise just fkn kill me dogg, I’m exhausted”.
After being attacked earlier in the night, she also messaged she had a knife and “just doesn’t care”.
Keene said the evidence police had been able to gather – including via texts and social media messages – revealed the days leading up to Rigby’s death were “quite an edgy time”.
“She’s involved in a number of confrontations involving not just Jimmy Heremaia, but other people as well,” he said.
“It’s a tragic set of circumstances. No doubt it would have been a pretty scary time for Rigby, which culminated in an absolutely tragic event.”
‘I need to get rid of this’
After picking up Rigby in the Napier suburb of Onekawa, the pair headed to Bay View, about 8km from Napier.
They travelled in a grey Toyota sedan, a vehicle the summary of facts says Heremaia had borrowed several days earlier from his Mongrel Mob captain “under the pretence of needing a car for work”.
Heremaia pulled the car over on a grass verge on Hill Rd near the semi-rural township.
Their presence was noted by a member of the public driving past, who secured a partial registration on her dashcam believing what she “had seen was suspicious and due to recent burglaries in the area”.
Not long after, Heremaia and Rigby had an argument in the car.
Rigby swung the hammer she was carrying for her protection at the gang member. The blow was blocked, before Heremaia overpowered the teen, took the hammer and delivered two fatal blows to her head.
Rigby’s body was put in the backseat of the car, with Heremaia driving towards Puketapu “in a panic, deciding what to do and where to dispose of Ms Rigby’s body”, the summary of facts said.
He also had conversations with Paul – via phone and text – before arriving at the then Mongrel Mob prospect’s home in Havelock North.
Police were later able to use CCTV footage and cellphone data to track Heremaia’s travels.
Paul later told police his friend had asked him for a change of clothes and petrol. The Crown’s summary of facts alleged Heremaia also showed Paul where Rigby’s body was in the car and said “I need to get rid of this”.
Heremaia changed out of his blood-stained clothes, while Paul headed to a service station and spent $70 to fill a fuel can.
The pair then travelled to the River Road Recreational Reserve in convoy in the early hours of Saturday, September 3. Heremaia parked his gang captain’s car, poured petrol on and throughout it, then set it alight.
The summary of facts says Heremaia then told Paul that he had earlier killed Rigby.
It was now time for Heremaia to destroy anything that linked him to Rigby’s death that the fire hadn’t been able to.
That included deleting a Facebook profile under a fake name from his phone that he had used to contact Rigby, unsending messages he had sent to Paul, and telling family to delete messages he had sent them.
By 3am on September 3, Heremaia had fled Napier, with family members taking him to Wairoa, 118km north up SH2.
He also sent a series of messages to family and associates – including those linked to the Mongrel Mob – that he was still looking for Rigby so he could recover his gang shirt.
He told his immediate gang leader he was “still looking for that b****”, the car he had been loaned had broken down and then been stolen.
Messages also included him being in Wairoa, something the summary of facts says was a bid to create an alibi that he was out of town when the teen was killed.
As Heremaia was trying to cover his tracks, locals living near the River Road Recreational Reserve started contacting police about the discovery of a burned-out car.
In a breathtaking mistake, the officers who attended the callout mistook Rigby’s remains in the car for a burned animal, and left them unattended in the reserve.
It wasn’t until two days later - on the day a tow truck was booked to take the vehicle to a wrecker’s yard - that police returned to the scene on the urging of a dog walker who had looked into the car, recognised human hair, and realised they were looking at human remains.
Police later apologised to Rigby’s family for their error.
A wanted man: It took police just two weeks to zero in on Heremaia
Keene was put in charge of the investigation – which was initially deemed an “unexplained death” - on September 5, the day the charred body was identified as human.
Three days later Rigby’s Auckland-based older sister was becoming increasingly worried about a lack of communication from the 18-year-old, with Anaherā Rigby posting on social media: “come home please. Call me. Text me. Whatever just let me know your [sic] ok.
“For days I have been looking for you. I need to know where you are sister. I need to know you’re safe. I can’t sleep. I can’t eat. Please come home.”
On September 9, the inquiries were upgraded to a homicide investigation, dubbed Operation Sphinx.
But still the identity of the remains was not known.
That answer came on September 13 when police confirmed the body was Rigby’s.
It was a confirmation that Anaherā knew deep down was coming, telling the Herald: “I was dreaming of her ... she was telling me it was her.
“I actually wasn’t surprised once they [police] told me it was her. I’m her sister, [if she was alive] I would have already found her and I hadn’t ... I just knew.”
By the time the sickening news was delivered to Ariki’s family, Heremaia had distanced himself from the crime scene.
He messaged his partner, and mother of his children, that he had to leave Hawke’s Bay as “something bad gonna happen to me. I can feel it.”
He travelled south to Pahīatua to visit his sister, who then drove him to Taupō to meet his father. He headed north to South Auckland.
While he had fled Hawke’s Bay, he was firmly in the sights of police.
Keene said that within the first two weeks of the homicide probe, the Mongrel Mob member had become a “person of interest” to the investigation team; which featured about 30 staff initially.
Inquiries had linked him to the burned Toyota sedan.
CCTV footage obtained by police during the investigation was also able to track the car’s movements on the night of the murder, and in previous days when Rigby and Heremaia had been filmed in Wairoa together.
“Our task was to build a case of him as a suspect,” Keene said.
As Rigby’s family prepared to farewell the teen at her funeral in Hastings on September 16, Heremaia had an unexpected visit from police officers in Auckland.
“He denied his involvement at that stage,” Keene said.
“We weren’t in a position to lay charges. It was the early stages of the inquiry so we had to continue to build a case against him.”
Apart from some sporadic and brief visits to Hawke’s Bay – when he always travelled at night - South Auckland was to remain Heremaia’s home until his later arrest.
Paul was also about to be visited by Keene’s investigation team, having been caught on CCTV driving through Havelock North on the night Ariki died in his father’s car in convoy with the car Heremaia was driving.
When questioned, he told officers Heremaia had asked for a blanket, clothes, and petrol, and that he later saw the car Heremaia had been driving in flames.
But for two years, Heremaia remained at large.
Repeated pleas from police and Rigby’s family urged anyone with information to come forward to the investigation team or anonymously to Crime Stoppers.
As time dragged on, some family members became frustrated with what they believed was a lack of progress.
But Keene stressed although police were adamant they had identified the person responsible for Rigby’s death, and told the family they were making progress, they were limited in what details they could actually share.
“I was always confident that we were going to get Mr Heremaia,” he said.
“The main reason we needed to build a significant evidential case against Mr Heremaia [was because] we know we only get one chance once we arrested him.
“If there was to be a trial, all that evidence would have been played out in court. We needed to make sure that it was up to such and such a value that were going to be all but assured of a conviction.”
A large amount of information did come to the police following the numerous appeals.
The gang involvement aspect of the homicide created challenges in getting information.
Keene said police appreciated how challenging it could be for people to share information that could incriminate offenders with gang links.
“We fully appreciate it’s quite simple for me to sit here and say you need to do the right thing,” he said.
But Keene said police also had to understand that it took courage for a member of the public who lived in the same communities as gang members – or came across them in other ways in their daily lives – to come forward with information.
“People are hesitant to speak to the police in relation to these types of things when they know there’s gang involvement,” he said.
As time went by, the Operation Sphinx team reduced to about seven officers.
While Keene and his comrades also juggled other cases, he had a steely focus to do whatever he could to solve the case.
Not a day went by in those two years when the case wasn’t discussed or thought of.
“We all have one thing in common, and that’s the tenacity to achieve a result,” he said.
And Keene said he always remained confident Heremaia would end up behind bars, and there would be justice for Rigby’s family.
“We had put some overt pressure on him through media, and through various other techniques, to sort of put the pressure on him in order to say, ‘We haven’t gone away, Jimmy, we’re not going away and we never will go away’.”
‘Icing on the cake’: How the investigation team reacted to confession gained by undercover officers
It was two years after Rigby’s remains were identified that the confidence from the senior Hastings-based detective was proven justified.
The Operation Sphinx team was contacted by the detective running “Luke” and the “Boss” that Heremaia had confessed to killing Rigby.
The audio, and a written transcript of the conversation, was sent to the investigation team based at the Hastings Central Police Station.
Not only was the confession welcomed, but so too were the details that Heremaia provided, which tallied with the vast body of evidence Keene and his team had gathered.
“Jimmy Heremaia had backed up all that information and all that evidence by what he had disclosed to the undercover officer,” Keene said.
“Things such as location of the death, of the scene, certain circumstances around what he did afterwards . . . it was the icing on the cake. It was well received, to say the least.”
Detectives from Hastings then flew to Auckland, where Heremaia was arrested on September 17, 2024.
Despite putting his heart and soul into the case for two years, Keene wasn’t there to take Heremaia into custody.
He was on holiday in Austria, having been notified of the significant development by a colleague via an early morning WhatsApp message.
“To say the least, it was an extremely satisfying and jubilant day.”
Keene’s colleagues later shared with him what happened when they put Heremaia in handcuffs.
He was told the now-jailed murderer was “quite sombre” when police read him his rights.
“I believe in my mind that he probably knew deep down that we were coming,” he said.
“My understanding from the team that went up and arrested him is that he was almost resigned to his fate.
“I can’t speak for Jimmy Heremaia but what I can say is that no matter who you are . . . it [committing a murder and keeping it secret] takes a toll on an individual.
“He kept that secret virtually to himself for nearly two years. As we know, he did inform somebody of it. And it just happened to be an undercover police officer, which was fortunate for us.”
‘It does leave a lasting impression on you’: Detective on the human side of police work
Heremaia pleaded guilty in the High Court at Napier on February 28 to murder and arson.
Keene said knowing Heremaia would now face justice for his callous offending provided a “huge sense of satisfaction” for the police investigation team and Rigby’s family.
“They put their trust in us and let us do our job,” Keene said.
“They deserved to know what happened to Ariki.”
He thanked the Rigby family for being patient during a “long two years”.
“There were times when we would ring to update and we didn’t always have something substantial to say, except to say that we believe that we were moving forward with the investigation,” Keene said.
“And I know that was frustrating for them on occasions.”
Keene also thanked the members of the public who provided information to the police, including “little snippets” of information that could have helped build the case against Heremaia.
“I know it wasn’t easy for a lot of people,” he said.
“The witnesses that did come on board that did sign statements for us, we know it wasn’t easy for them. This case does show that if people do come forward and do the right thing, the police can effectively do their job.”
Keene is also acutely aware that Heremaia wouldn’t be behind bars if it wasn’t for the dedication and professionalism of the various police staff who worked on the case.
That includes those officers assigned to Operation Sphinx, other staff across Hawke’s Bay, officers in Auckland and Wellington and the undercover officers and their handlers.
“They should all be, and I know they are including myself, very proud of all the efforts that were put in and the ultimate result.”
But it was a conviction that came with a lot of “pressure” on the whole investigation team, with Keene adding it was “quite taxing” at a human level.
Many of the officers would have had families themselves, some potentially with daughters or nieces around the same age as Rigby.
Given the nature of the crime – and the crude way in which Heremaia tried to dispose of her body – Keene said it did have an impact on those charged with finding the teen’s killer.
“It’s a balancing act. Yes, you’re right, we all are human, we all have emotions and we think about things differently,” Keene told the Herald.
“This case was quite telling in the effect of its circumstances right from the start. [It was] very challenging emotionally in some aspects because of the horrific way we know that Ariki ended up, and all the detail that we were privy to, but not everybody else was, which has obviously come out now to a certain extent.
“It does take a toll.”
The “responsibility” officers took on to catch Rigby’s killer – both to ensure the crime was solved and try and provide some comfort for her family – also took an “emotional toll”.
That only increased given the passage of time between her being identified and Heremaia’s guilty plea.
“This went on for the best part of two years,” Keene said.
“To be quite frank with you, it probably won’t leave us for some time when you put so much effort into one case.
“It does leave a lasting impression on you.”
Neil Reid is a Napier-based senior reporter who covers general news, features and sport. He joined the Herald in 2014 and has 33 years of newsroom experience.
