Police responding to a deadly hostage crisis in a Sydney cafe underestimated the threat the gunman posed and should have stormed the building earlier, a coroner has said.
New South Wales state Coroner Michael Barnes issued his findings on Wednesday after a 2.5 year inquiry into the 2014 siege at the Lindt Cafe in central Sydney.
The conclusions follow intense criticism from several of the 18 hostages and families of the victims, who have long questioned why police waited nearly 17 hours to enter the cafe.
Police only moved in after an erratic Man Monis fatally shot cafe manager Tori Johnson.
Monis was then shot dead by police and another hostage was killed in the crossfire.
Though Mr Barnes took pains to say that the only person responsible for the deaths was Monis himself, he concluded police made a series of mistakes.
The most notable error was failing to immediately storm the cafe after Monis fired at a group of hostages who fled the building around 16 hours into the crisis.
Another 10 minutes elapsed before Monis fired his shotgun into the back of Mr Johnson's head, killing him instantly and finally triggering the police response.
"An emergency action should have been initiated following the first shot of Monis at 2.03am," Mr Barnes said.
"That made it clear there was little to no chance of resolving the siege, and those within the cafe were at an extreme risk of harm.
"The 10 minutes that lapsed without decisive action by police was too long. Tori Johnson was executed in the meantime."
The attack unfolded in the most unlikely of places - a cheerful chocolate cafe in the heart of Sydney, at the start of a workday and just a week before Christmas.
Australians were horrified and bewildered by the tragedy, and demanded to know how such a thing could have occurred in their normally placid city.
Mr Barnes summarised the horror of the attack in his findings, saying the terror the hostages felt was akin to torture.
"Monis oscillated between feigning regard for their welfare and threatening to blow them apart," he said.
"They had entered a familiar environment only to find it transformed into a prison run by a vicious maniac."