"Window 2, hostage down."
They were the words Police sniper Mark Davidson never wanted to say on the night of the Lindt cafe siege.
Those four words meant the New South Wales Police had allegedly failed in their primary objective on December 16, 2014 — to prevent any of the people taken hostage by Man Haron Monis from being killed.
Cafe manager Tori Johnson was executed by Monis. Customer Katrina Dawson died when she was hit by fragments of police bullets when they stormed the cafe, in Sydney's bustling Martin Place, and killed the terrorist.
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Davidson, codenamed Sierra Three 1, spent 16 hours crouched in an office block metres away waiting for the moment to take the shot that would take down Monis.
He said he had a plan that, despite the many challenges that day, could have worked.
But, he said, alleged critical failings in the way the operation was run by Police meant opportunities to subdue Monis were missed.
"We could have saved Tori at least," Davidson told Australia's 60 Minutes on Channel 9 last night. "I believe Tori was a preventable death".
"Things occurred on that day I don't understand."
However the NSW Police has said Davidson's plan could have gone disastrously wrong. Besides, there was only one short period in the whole siege when there may have been a clear shot of Monis — and even that was debatable.
"The Coroner concluded that the decision not to fire was completely reasonable," said the Police on Sunday.
Killing a last resort
Davidson said he feels guilty that he wasn't able to save Johnson. The sight of his final moments still haunts him.
"Guilt's not always completely rational and it's magnified with the benefit of hindsight.
"I started having flashbacks of Tori dying over and over," he told 60 Minutes' Liz Hayes.
As it became clear on that an unprecedented terrorism situation was unfolding, Davidson said decisions were mad that baffled him.
He believed he would be taking on a co-ordination role for his fellow snipers. However he was sent into the field, which meant there was no sniper co-ordinator at the police command post.
Nevertheless, it was day he had trained for so he set up in a critical position — in the Westpac Bank building across the road.
Whether by plan or accident, Monis didn't make the snipers' jobs easy. He had a tendency to stay in the shadows of the cafe.
But even if he had placed himself neatly in the centre of a sunlit window, a decision to shoot is always agonised over, said Davidson.
"If you're going to kill someone first of all you need to justify an immediate threat to everyone.
"I know some people may say, well they were held against their will by an armed man that's the immediate threat satisfied there, but using lethal force also needs to be a last resort."
Getting it wrong could have serious consequences, even laying snipers open to murder charges he said.
Monis had also threatened to detonate a bomb, which could explode even if he was shot.
But as the day progressed, and some of the hostages escaped, it became clearer that the bomb was a furphy.
Davidson told Channel 9 that he never received that information which could have been vital in deciding whether to take a shot.
Later, there was a text sent by Johnson from inside the cafe that said that the terrorist was on his own away from the hostages. Again, it was information Davidson said he didn't receive.
At one point, Davidson said he was certain he had Monis in his sights. He could see someone wearing a bandana with Arabic writing on, which they knew Monis had donned.
"I didn't have any doubt it was him but people in the command post had a doubt." Police have confirmed others could not be sure it was Monis.
It was Davidson, and his fellow snipers who had the final say on shooting. And they had a plan in place to do so that would involve two shots. One to smash the glass of the office building and another, straight after, that would have killed Monis.
Tori's final moments
At just after 2am, six hostages escaped. It was a move that enraged Monis and set in play the attack's violent end stage.
Monis forced Johnson to his knees, a severe deterioration in events. Davidson said he sent this message to the command post but there is some conjecture as to whether it was received. Certainly, there seemed to be no change in his orders.
Then a shot rang out.
"I saw Tori flinch and his body was engulfed by an orange flash of light which I believed was the muzzle flash of the shotgun.
"He sits back up, doesn't turn around, doesn't attempt to look for an opportunity to charge him or rush him or get the gun," he said.
"That was quite remarkable. It was like he was resigned to his fate. That his soul had resigned itself to leaving his body at that time."
Then a third shot.
"I saw the results of it and that's when Tori died."
He immediately sent this awful news to the command post.
"Window 2 hostage down.
"I repeated it a number of times because I wanted to make sure I was being heard. And it was clear that someone had been killed and they needed to go."
Soon after this, police swooped into the Lindt cafe killing Monis.
Davidson said the operations could have been wrapped up long before Mr Johnson's death.
"I believe on the day we didn't as a collective play how we trained.
"There was an achievable option to shoot and kill Monis and save the hostages. It's upsetting because that's what we're there for."
In a statement on Sunday, NSW Police said there were severe doubts over whether a clean shot could be taken. There were also concerns as to the effectiveness of Davidson's plan.
"Breaching the Westpac glass and then shooting through it would have taken significant time and generated noise that could have been heard by Monis.
"This may have resulted in him retaliating in any number of ways such as detonating the (bomb) that was believed to be present.
"Breaching the glass would have created a network of fine cracks, which would have compromised Sierra Three 1's ability to see to take the shot."
The Police added there was only one small period when Monis may have been in a position to have been shot — between 7:38pm and 7:48pm.
"It is noted that Sierra Three 1 said in evidence he had no doubt it was Monis but was concerned that he did not have the legal justification to take the shot.
"The Coroner found that the snipers could not see whether there were any hostages immediately behind or beside the person and they were concerned that firing would endanger the hostages.
"The Coroner concluded that the decision not to fire was completely reasonable."