When police responded to a call about an armed man inside a luxury apartment block, nothing could prepare them for what they found.
Police were met by gunshots when they arrived at 141 Dorchester Avenue in South Boston on Friday, the $US1.9 million penthouse belonging to Dr Richard Field.
The shooter, 30-year-old Bampumim Teixeira, 30, missed the officers before they pumped multiple bullets into him, leaving him wounded but very much alive.
When officers searched inside, they found the bodies of Dr Field and his live in fiancee, Dr Lina Bolanos.
Their hands had been bound and their throats had been slit. Photographs of the couple had been cut up and scattered around the residence. Messages of revenge were scrawled on the walls, which were also splattered and smeared with blood, but police have refused to reveal what the messages said.
It looked like a deeply personal crime scene. A crime of passion.
Minutes before he was murdered, Dr Field managed to raise the alarm by texting a friend, saying an "armed man" had entered their apartment.
But investigators trying to determine a motive for the double homicide have since discovered that Teixeira was known to the two doctors and believe he entered their home with the couple's knowledge.
"(For) someone to come here, go up to the 11th floor, to the penthouse, we got to believe that somehow there was some type of knowledge of each other," Boston Police Commissioner William B Evans told reporters at the weekend.
Commissioner Evans said the building had tight security that required the use of a key to activate the elevator.
Dr Field worked at Boston's North Shore Pain Management clinic and Dr Bolanos was a paediatric anaesthesiologist at Massachusetts Eye and Ear Infirmary.
Revelations that the couple knew their alleged killer have sparked sordid rumours about the motive, with some speculating that Dr Field was involved in the illegal distribution of drug prescriptions and may have been killed after he refused a request from Teixeira.
Others have wondered if there was a sexual element to the murders, perhaps a love triangle gone wrong.
An ex-girlfriend of Teixeira, a former security guard who had just finished a nine-month sentence for robbing two banks, revealed that he had confessed to her he "did not have long to live" during the last conversation they had before the murders.
She told the Boston Globe that he had sounded "strange" when he called her on April 22, shortly after his release from jail.
He said his death was imminent but insisted he was not suicidal. He welcomed her offer to pray for him, saying: "Yeah, I need prayer".
Teixeira had also hinted at something darker, telling her: "I am not a good person" but she said it never occurred to her that he would hurt anybody.
The ex, who asked to remain anonymous, wept as she described Teixeira as "charming" and a "gentleman" who was kind to her nine-year-old.
Bolanos was a paediatric anaesthesiologist at Massachusetts Eye and Ear Infirmary. She was also an anaesthesia instructor at Harvard Medical School.
Massachusetts Eye and Ear Infirmary released a statement from the hospital's CEO John Fernandez, who said: "Dr Bolanos was an outstanding paediatric anaesthesiologist and a wonderful colleague, in the prime of both her career and life."
Dr Sunil Eappen, chief medical officer and chief of anaesthesia at Massachusetts Eye and Ear, said in a statement on the hospital's website that he first met Bolanos when she was a young researcher.
"We have worked together since 2011, except for a short break when she moved to Texas for a few months," Dr Eappen told AP.
"I watched her mature and blossom from a young medical school graduate to a fabulous experienced paediatric anaesthesiologist."
Dr Eappen said she performed her job with both great skill and compassion.
"Everyone at Mass. Eye and Ear really loved her," he said. "It is desperately hard for all of us to fathom that our friend who never failed to brighten our days is no longer with us."
On its website, North Shore Pain Management said Dr Field was "instrumental in the creation of this practice."
"He was a valued member of the medical community and a tremendous advocate for his patients," the statement said. "His tragic and sudden passing leaves an inescapable void in all of us."