Police officers outside the cafe, guns at the ready, moved back. Nine minutes of silence followed, and then all hell broke loose on Martin Place.
At 2.13am a second shot was fired and a sniper positioned in a building opposite the cafe reportedly yelled "hostage down".
Police advanced, using flash bang stun grenades to try to disorientate and subdue Monis.
As they converged on him he is said to have screamed at officers: "look what you've made me do" seconds before he was gunned down.
And then, it was all over. Three people were dead, including the gunman, and the mountainous task of piecing together the why, what and how began.
An hour before the siege, Monis was filmed by security cameras walking calmly through Martin Place. Wearing a backpack he strolled up and down the busy pedestrian mall as it filled with workers getting ready to start their working week.
Monis went into the cafe, sat down and ordered coffee. He chatted with manager Tori Johnson, neither he or the bag at his feet drawing any untoward attention.
Suddenly he stood, drew a short-barrelled shotgun and screamed at customers to stand with their hands up.
He was a representative of Islamic State and this was a terrorist attack, he told them.
There were bombs in the building, they must do what he said.
He walked to the cafe's door, locked it and the terrifying ordeal began.
Police were alerted almost immediately, when a woman banged on the door of the cafe trying to get in. Monis waved his gun at her, indicating clearly what was going on inside.
Panic set in, the area was evacuated and police surrounded the cafe.
For the next 16 hours Sydney waited to see what Monis would do next.
The Guardian newspaper in Australia has pieced together what happened inside during that time, based on survivor stories.
When it began, some hostages screamed, others cried and at least one began to vomit in fear.
A cellphone rang and when it was answered, Monis screamed at the hostage, "Drop that phone".
Monis must have feared losing control - he was one man, and even though he was armed, he had 17 people to keep in line.
"The gunman was surrounding himself with the staff from Lindt forcing them to stand near him, he was using them to control the social media, to get his message out, a source told the Guardian.
"He was directing them on what to do, who to call, what to say.
"The other people, the older people, he pushed to the other side of the shop, he kept them there."
Monis forced cafe staff to call newsrooms across Sydney and relay his demands.
Journalists who took those calls could hear the manic Monis barking commands in the background.
He had three demands. The first, in exchange for an on-air live broadcast phone call with Tony Abbott, Monis would release five hostages. The second, in exchange for a public declaration from the Government that his was an act of terror committed on behalf of Islamic State, he was prepared to release two more. The third, for a black Islamic State flag he was prepared to release a final prisoner.
Authorities refused to engage and he had to rethink his strategy. He turned to social media to disseminate his demands, forcing the terrified hostages to appear in video messages which were then posted on websites.
He selected four female hostages to preach for him. At his direction the women called him "brother" and appeared to be reading a written list of his demands held just off-camera.
Bank executive Marcia Mikhael, 42, was forced to post Monis' message on her personal Facebook page.
"Please help," she wrote from inside the cafe.
"The man who is keeping us hostage has asked for small and simple requests and none have been met. He is now threatening to start killing us. We need help right now."
As Monis realised his demands were being ignored, his fury boiled to a head.
"There was no reasoning with him, he was so angry," said one hostage, who spoke to the Guardian on the condition of anonymity.
"He knew his message was not getting out, and he was getting angrier and angrier."
Other hostages told the newspaper that amid the madness there were moments of "calm and conciliation".
They were allowed to drink water, one woman was permitted to take her medication and they could use the toilet - but only when escorted by a Lindt staffer selected by Monis.
As the hours dragged on, the pressure was building inside the cafe. Monis' nerves were beginning to fray and the hostages grew bolder and began to beg for their freedom. They wanted to go home and see their families, they'd had enough.
At 3.37pm, six hours in, the siege took a dramatic turn. While going to the toilet a group of men passed a door with a release button. One push of that button and the doors slid open, giving them their chance to escape.
The Lindt staffer on toilet escort duty also fled through a nearby fire door. Two more Lindt employees would escape through that same door just after 5pm.
As the number of hostages dwindled, Monis unravelled further and he was seen shouting at hostages. As Sydney darkened, he shut off the cafe lights, making it impossible for anyone to see anything inside.
The hours passed slowly. Australia held its breath, the police held their position, all waiting for something but not knowing exactly what.
At 2am came the beginning of the end.
Cafe worker Joel Herat was among the hostages who made that sudden break. After helping a pregnant colleague out of the building he tried to call Mr Johnson. He could not get through. He didn't know it, but his manager and friend was already dead.
"I don't know how they did it ... the moment they busted that door down, Joel heard shots in his proximity," his father told the Age newspaper.
"It had to be immediate, no opportunity to look back ... they just had to take their opportunity."
Metres down the road, Mr Herat's parents was waiting in a room set up for hostages' families.
When they heard the first gunshot, his father said, "everybody surged towards the street" but were held back by police.
"Everybody in that room let out an awful sigh and a bit of a wail ... It sounded like instant fire but it was the flash grenades that were going off initially and then moments after that we knew there was bullet fire and it went on for a long, long time."
Mr Herat said later: "Mum if we didn't get out [then], we were going to die."
What happened in that last 10 minutes is under intense investigation and five days on there are still more questions than answers.
It is thought that the first gun shot that pierced the still of Martin Place was a warning shot.
The second claimed the life of Lindt manager Tori Johnson as he wrestled Monis for the pump-action shotgun and the freedom of the 12 other remaining hostages.
In the manic finale, to the soundtrack of rapid gunfire, flashing lights and billowing smoke, 38-year-old barrister and mother-of-three Katrina Dawson was fatally shot alongside Monis.
She was soon hailed a hero when it emerged she lost her life trying to protect her pregnant friend and workmate Julie Taylor from the gunfire that ended the siege.
Four others were wounded in the gunfight, including a policeman hit in the face with shotgun pellets and 75-year-old woman shot in the shoulder.
Cafe killer: Five key questions
Why was he out on bail?
Man Haron Monis was free despite facing 40 sexual and indecent assault charges and allegations he was involved in the murder of his former partner, Noleen Pal. Stricter bail rules will be introduced in late January, which the NSW Government insists will mean people like Monis will be kept behind bars.
Why was he granted asylum?
Allegations have surfaced that Monis fled his native Iran in 1996 after embezzling US$200,000 ($256,991) of his clients' cash while working at a travel agency. In Australia he was granted political asylum - something Iran now says was a cover for crimes back home.
Why wasn't he extradited?
Iranian authorities say they tried unsuccessfully to have Monis extradited in 2000 to face his embezzlement charges but Australia turned down the request as the two countries don't have an extradition agreement in place. The Iranians have now pointed out that the Lindt cafe siege may never have happened had Australian authorities co-operated with their request more than a decade ago.
Why wasn't he on a watchlist?
As more details of the siege came out on Wednesday, authorities were under increasing pressure to explain how Monis, a man with a long criminal history and links to extremism fell off ASIO's watchlist. He had been on the list in 2008 when he sent offensive letters to the families of dead Australian soldiers, but dropped off some time after that.
How did he get a gun?
Regardless of whether Monis ever had a gun licence or not, he was just like so many other criminals who manage to illegally get hold of a gun. Court documents in 2011 say Monis held a gun licence through his work as a security guard but it had expired. Prime Minister Tony Abbott wanted to know how a man with Monis' record held a gun licence. But the Federal police and NSW Police say there were no records of him ever holding a licence.
- AAP
