About 9.30am on Monday, barristers Katrina Dawson and Julie Taylor popped into the Lindt Chocolat Cafe. The pair worked together in commercial law, around the corner at the prestigious Eight Selborne Chambers next to the Supreme Court.

Ms Dawson, a 38-year-old mother of three young children, and Ms Taylor, pregnant, were among nine customers and eight staff inside that small cafe in Martin Place. They were there with Stefan Balafoutis, another young member of the NSW bar, from the 10^th Floor Selborne/Wentworth Chambers.

There were some familiar faces in the crowded room: Elly Chen, their smiling barista, a 22-year-old student from the University of NSW; Tori Johnson, the cafe's affable 34-year-old manager, and 30-year-old Harriette Denny, from the Sunshine Coast but working at the cafe in Sydney. A 75-year-old woman and a man in his 80s were also among the customers.

Then, through the cafe's automatic glass sliding doors, entered a bearded 50-year-old man. This was Man Haron Monis. He was wearing a bandanna and carrying a blue bag that contained a shotgun.

The staff and customers could not have understood why Monis disabled the automatic glass doors, so nobody else could  enter.

They had no clues to his antecedents: the refugee who had fled from Iran to Australia in 1996, claiming he was persecuted for his liberal take on Islam; who became a self-proclaimed spiritual healer, peddling astrology and black magic, and a self-anointed sheikh; who would renounce his Shia roots to become a Sunni; who would be convicted of harassing the families of Australian soldiers killed in Afghanistan and an Austrade official who died in the Marriott Hotel bombing in Jakarta; who was on bail for his alleged complicity in the brutal murder of his former wife.

Suddenly Monis ordered the 17 other people in the cafe to get on the floor. A woman trying to enter from Martin Place saw this happening. She called police.

A minute or so later, at 9.45am, a staff member called Bruno arrived for his shift but he also could not enter. He watched what was happening through the glass.

Soon the terrified face of  Ms Chen appeared. She was pressed against the glass and, on Monis' orders, holding aloft a black flag scrawled with Arabic text in white, which translated as: "There is no god but Allah. And Muhammad is his messenger."

Police began to evacuate Martin Place of thousands of people. Channel Seven's news teams, in their studio opposite the cafe in Martin Place, were evacuated but their camera kept running on the action.

The startling images of Ms Chen and other hostages, the palms of their hands pressed against the glass, were beamed around the world.

Monis identified himself to his hostages as The Brother. But while police evacuated surrounding city blocks, nobody knew quite what the hostages were enduring inside the cafe.

Among them were four staff from the Westpac building across the mall. They included project manager Marcia Mikhael, a 43-year-old mother of three from Glenwood, in Sydney's north-west.

The stakes became clearer when posts appeared on her Facebook page on Monday afternoon. "Dear friends and family," Ms Mikhael wrote. "I'm at the Lindt Cafe at Martin Place being held hostage by a member of the ISI [Islamic State].

"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. The man wants the world to know that Australia is under attack by the Islamic State."

But about 4.35pm there came hope. Two of the hostages, Stefan Balafoutis and the man aged in his 80s, ran from the cafe, escaping through the automatic doors.  Soon after, a cafe worker fled through a service door. And just before 5pm, two women, Elly Chen and fellow cafe worker Bae Ji-eun, a 20-year-old Korean student, escaped.

Inside the cafe, however, this only infuriated Monis. The youngest of his captives, 19-year-old Jarrod Hoffman, from Bondi, called radio 2GB and The Daily Telegraph to relay Monis's demands: he wanted a direct line to Prime Minister Tony Abbott and an Islamic State flag delivered to the cafe.

"He says an eye for an eye," Mr Hoffman said. "If someone else runs, someone dies."

He added: "I have had a shotgun put at my head. Yes we do need help, but that will only happen if demands are met."

Media complied with police requests not to publish these messages or Monis's demands while the siege continued. Monis was using the hostages to get his word out, and police did not want anyone playing into his hands.

But he persevered. He ordered hostages to deliver video messages shot on a smartphone. These were posted on Monday evening using the YouTube account of another hostage, 21-year-old Joel Herat, a staff member at the cafe. YouTube took down the videos, but they spread on social media.

"Hi everyone, I'm Selina Win Pe," said Ms Mikhael's colleague, from Westpac's global transformation project. "We have three specific requests and none of these have been met.

"One is to send an IS flag as soon as possible and one hostage will be released. Two, please broadcast to all media that this is an attack against Australia by Islamic State.

"And number three is for Tony Abbott to contact The Brother on a live feed and five hostages will be released.

"Most importantly, there are three bombs around George Street, Martin Place and also at Circular Quay and in order for these not to be ignited we need these three things to be met as soon as possible," Ms Win Pe said. "Please help us."

Similar video messages were delivered by Ms Mikhael and barrister Julie Taylor, who began, "This is a message to Tony Abbott".

But Ms Win Pe became more desperate in a call to the Telegraph, pleading: "We've got pregnant ladies in here and sick and elderly … We have not heard from Tony Abbott. We have been asking him to call us to have a long conversation. He clearly doesn't give a shit because he hasn't called us since 9.45 this morning … Help us. Help us to get Tony Abbott to call this gentleman to send the fricking Islamic State flag …"

The demands were not met.

But at 2am, more than 16 hours after the siege began, it appears the 12 remaining hostages seized their chance. Monis began to drift off to sleep. They dashed for the exit.

Monis roused and started shooting. Tori Johnson, the cafe manager, attempted to wrestle the gun from him. Monis shot him dead, although Mr Johnson's wounds suggest he beat him severely before firing the fatal shot, one source said.

At 2.03am, six of the hostages ran out a service door. They included Harriette Denny, Jarrod Hoffman and software engineer Viswakanth Ankireddy, a 32-year-old from India who is living in Sydney with his wife and young daughter and working on a Westpac project.

Outside, police had heard the shots. And a sharp-shooter had seen Mr Johnson go down, one report said. Now they had to storm the cafe or many more people would die, Police Commissioner Andrew Scipione said later.

About 2.10am they shot down the glass doors and blazed into the cafe in a hail of gunfire and lightning flashes of light.

In those final seconds, they killed Monis. But the barrister Katrina Dawson – mother of three, and Julie Taylor's coffee companion – was also killed in the firefight. Police believe it was Monis's bullet that killed her.

Injured in those final violent seconds were Marcia Mikhael, shot in the leg, the 75-year-old woman, shot in the shoulder, a 52-year-old woman who was shot in the foot, and a 39-year-old policeman whose face was sprayed with pellets. He was released from hospital and Deputy Commissioner Catherine Burn said: "His only words to me were, 'I'll be back at work tomorrow'."

Fifteen hostages were alive, but Ms Dawson and Mr Johnson became the victims of Man Haron Monis, a deranged lone wolf who wanted the world to believe he was an Islamic State warrior.

He had been born with the name Mohammad Hassan Manteghi.  He grew up to become a fake sheik, a pretend spiritual healer and a wannabe terrorist.

Nobody believed him. But he was dangerous and, for more than 16 hours, he did terrorise a nation.