Jarrod Morton-Hoffman mouthed "I am going" to his fellow hostages moments before he led the charge out of the Lindt cafe and gunfire cracked above his head.

In compelling detail, Mr Morton-Hoffman, 20, has recounted to an inquest how he fled the Martin Place cafe as the siege reached its 17th hour in December 2014.

It was about 2am when gunman Man Haron Monis took two hostages - Selina Win Pe and Fiona Ma - with him towards a rear fire exit.

It came after Monis grew increasingly paranoid about police trying to enter the cafe through the back exit.

Mr Morton-Hoffman told the inquest he was worried that, if Monis did open the back door, he would see the business cards Mr Morton-Hoffman had used to draw a map and write notes to the police.

After Monis moved out of sight, Mr Morton-Hoffman turned to the remaining group of hostages and said in a loud whisper, "I'm going."

"It was 2am, I felt like our attempts at placating Monis were finished; this was the first time he left the room," he said.

Seconds later, Mr Morton-Hoffman turned around and quickly pushed the doors of the cafe open and sprinted.

"I believe I heard the sounds of glass smashing on the ground," he told the inquest on Wednesday.

"By this time, I had run around the corner and was running towards the automatic doors.

"I heard Monis scream, 'What was that?' "

As Mr Morton-Hoffman tried to prise open the glass doors leading onto Martin Place with his hands, he heard fellow hostage Joel Herat scream, "He's chasing us."

Mr Morton-Hoffman said he went to press the emergency button, which opened the glass doors.

He said he saw the rest of the hostages behind him and heard the crack of a gunshot and the spray of debris.

The inquest has previously heard that Monis fired the shot at the hostages as they fled but missed.

In line with the courage and calculated planning displayed throughout the siege, Mr Morton-Hoffman said he chose to run at a wide angle out of the cafe and onto Martin Place to help police get a clear shot of Monis.

He thought if they ran wide, the police officers would be able to gun down Monis without hitting the hostages, the inquest heard.

Mr Morton-Hoffman had earlier seen four or five police officers with guns drawn waiting outside the cafe.

He assumed Monis had not seen them as "he would have opened fire".

"If he had seen heavily armed police officers within metres of the cafe at that point in time, especially in his emotional state, that would have been the final straw," he told the inquest.

Hostages barrister Katrina Dawson and cafe manager Tori Johnson as well as Monis died in the siege.

The inquest heard more examples of Mr Morton-Hoffman's leadership in dealing with Monis, including trying to placate him as he grew increasingly paranoid and erratic.

When he burst out of the cafe at 2.03am, Mr Morton-Hoffman was followed by five hostages, including barrister Julie Taylor.

When Ms Taylor was being held hostage inside the cafe that day, she was meant to be finding out whether her unborn baby was a boy or a girl, the inquest heard.

As Monis toyed with the hostages, saying that he would release one of them if they spoke to Amnesty International, Ms Dawson, tried to use Ms Taylor's 4½-month pregnancy as a means of persuading Monis to let her go.

However, Mr Morton-Hoffman believed that Monis' proposal would not become a reality.

"It was almost as if he was toying with the hostages," he said.

Ms Taylor escaped and Ms Dawson stayed behind. She died that morning after being injured by an errant police bullet when tactical police stormed in.

Moments earlier, Monis shot and killed Mr Johnson.

Mr Morton-Hoffman said Monis' behaviour throughout the ordeal flicked like a switch and described the hostage taker as amateur.

However when Monis first arrived at the cafe on the morning of December 15, waitress and university student Fiona Ma remembered him as amiable.

Ms Ma, who is studying dentistry in Queensland, had been working at the Lindt cafe for only about a week before the siege unfolded.

The 20-year-old served Monis as he sat down for a hot drink and a piece of chocolate cheesecake at table 40.

After he moved tables and asked to speak the cafe manager, Ms Ma said that Monis said in a loud booming voice: "This is an attack and I've got a bomb."

When Ms Ma later walked past Mr Johnson, whom she remembered as very respectful and a nice manager, he appeared red-faced and was talking on the phone.

"He seemed calm and stressed out at the same time," she told the inquest.

The inquest heard that Monis at one point claimed Australia was committing war crimes by not bargaining with him.

He wanted a hostage to go out and speak to Amnesty International or a related organisation because he believed he had a case against Australia, Mr Morton-Hoffman said.

When the hostages were creating videos at the behest of Monis, the gunman made jokes about being a director.

He also joked about people believing that an Indian man, who was being held hostage and held up a flag in the video, would be suspected of being the terrorist.

As Monis mentioned his need to smoke, Mr Morton-Hoffman said he considered a plan to trap him in the cafe freezer.

"He would just need to Gladwrap the one sprinkler in there and we could close the door on him," he told the inquest.

However the gunmen ended up blowing smoke into a bottle.

Monis also made the hostages fetch him a bottle in which he could urinate as he sat at a cafe table.

A hostage asked Monis what he was going to do after the siege and he claimed he had a plan but didn't detail it.

"I can't recall him ever saying 'I'm going to get out of this alive or I'm going to get out of this cafe,' " Mr Morton-Hoffman said.

The inquest continues.