About 30 minutes later, two female hostages appeared at the cafe window with a black and white flag bearing the Islamic creed or Shahada.
Other hostages were also directed to the cafe's Christmas-themed window and faced the street, some with their hands in the air.
As the day wore on, some hostages were told by their captor to contact media outlets and post messages on social media. In videos uploaded to YouTube, four female hostages - including 42-year-old bank executive Marcia Mikhael and Selina Win Pe - read demands made by Monis, who they referred to as "brother".
Ms Mikhael was forced to post the demands on her Facebook page. "Dear friends and family, I'm at the Lindt cafe at Martin Place being held hostage by a member of the ISI [Isis, Islamic State]. The man who is keeping us hostage has asked for small and simple requests and none have been met. He is threatening to start killing us. We need help right now."
Fiona Ma used social media to reassure her loved ones she was okay. "I'm getting your messages everyone!! Thank you, you beautiful souls," she posted on Facebook.
Another hostage was able to text message his mother about 3pm to tell her where he was. "My heart stopped, I sent back a text message: 'What is going on? Are you OK?'," the woman told 2GB radio station. His reply was: "I'm OK mum, can't talk".
At 3.45pm, with Monis' concentration elsewhere, three men made a daring escape from the cafe. John O'Brian, 83, was the first out, followed seconds later by lawyer Stefan Balafoutis and another man.
Cafe barista Elly Chen and a female worker followed the trio's lead less than two hours later, running from the cafe in their brown aprons, faces full of fear, their arms in the air. They were met by police near the cafe's exit and bundled to safety.
Clearly angered by losing five people, Monis forced two hostages to make phone calls to media with further instructions, including a demand for an Isis flag to be delivered and an audience with Tony Abbott.
One of the hostages also detailed the gunman's stark threats as he grew more aggravated. "He says an eye for an eye, if someone else runs, someone dies," Jarrod Hoffman told the Daily Telegraph. "We are all afraid, I don't think you have ever had a shotgun placed at your head."
Clearly terrified, the call finished with: "He's coming now. Bye."
Ms Win Pe, the second hostage to make contact with the Daily Telegraph, described a dire situation.
"The brother has looked after us all, we are all very, very tired," she said. "We've got pregnant ladies in here and sick and elderly and the very, very young staff who deserve to have a decent, normal life."
Ms Win Pe pleaded for a video Monis had to be published.
"He is sitting right here. I have you on speaker. I can't compromise myself and my fellow hostages. Get us out of here. Publish the video. He's not speaking to anyone. He wants to speak to Tony Abbott."
As the lights went out in the cafe about 9pm, the 12 remaining hostages were unsure what lay ahead.
Police said they were continuing negotiations and warned that the siege could last hours or days. But the final turn was near.
About 1.50am, Monis appeared to have become agitated, according to Seven news reporter Chris Reason.
"He didn't know what to do with them [hostages]," Reason told the network's morning programme. "He was sort of corralling them down one end and then down the other and moving around sort of randomly."
With their captor's eyelids becoming heavy about 2am, a group of five hostages ran for their freedom in what police called a "bomb burst", followed by a sixth.
Reports say cafe manager Tori Johnson, 34, leapt into action - bravely trying to wrestle the gun from Monis and pin him to the ground as the others fled.
Monis opened fire.
Across the road at the Channel Seven offices, a police sniper called out: "Hostage down. Window Two," the Telegraph reported.
As police moved in with heavy gunfire and blasts from stun grenades echoing from the building, Mr Johnson lay mortally wounded.
Katrina Dawson, 38, a barrister and mother-of-three, was the second hostage killed. Reports indicate she was protecting her pregnant friend and colleague Julie Taylor from the firefight. They had met for coffee.
Mr Johnson's colleague Bruno Filletti posted a tribute on Facebook, telling how he tried to enter the cafe to start work at 10am but the door had been locked.
He said his manager, Mr Johnson, had "sacrificed himself" to save others. After the hashtag #hero, he wrote: "The only word that can be used to describe Tori. He died trying to save another's life. He sacrificed himself to save everyone. You may be gone but never forgotten my friend. Rest In Peace."
Watching from across the road, Reason estimated the exchange of gunfire lasted 34 seconds but said the scene was chaotic with smoke from the flash-bangs and gunfire. It was followed by silence, cries for help and people screaming, particularly a woman.
Shortly afterwards there were more reports of gunfire or flash-bangs, apparently as police made their way to offices at the back of the cafe, before the gunfire ceased and the remaining hostages were evacuated to waiting ambulances.
Several of the wounded were brought out of the cafe on stretchers. Ms Mikhael, who had blood running down her leg, was carried out by police officers. Two other women hostages suffered gunshot wounds, while a 39-year-old police officer was hurt by gunshot pellets to his face. He vowed to return to work today.
Monis was also killed in the dramatic end to the central-city standoff.
Shortly before 3am, about 16 hours after the siege started, police officially confirmed that it was over.
KEY DEVELOPMENTS
• Police execute a search warrant at a house in southwest Sydney where Man Haron Monis is believed to have lived before the seige
• Australian Prime Minister Tony Abbott demands answers on why Monis was not on any Government terror watch lists.
• Hundreds of floral tributes laid at a memorial for hostage victims on Martin Place.
• Family of Tori Johnson, fatally shot after wrestling with gunman Monis, release statement paying tribute to the 'most amazing life partner, son and brother'.
• Colleagues of respected NSW barrister Katrina Dawson, also killed during the siege, describe her 'one of our best and brightest barristers' in a statement from the state's bar association.
• Images, footage and recordings of phone calls and messages made by hostages during the siege emerge.
• NSW police say they entered the cafe building after hearing gunfire. 'They made the call because they believed at that time if they didn't enter it would have been many more lives lost,' commissioner Andrew Scipione said.
