Glass poured down onto the ballistic shield bearer, the first police officer into the Lindt cafe. Then he saw the gunman, Man Haron Monis, in the back corner.

A burst of light - duller, more yellow than the flash-bang distractors - came from Monis' direction. Moments later, a red laser sight trained on Monis' chest travelled to his head.

The shield bearer, known as Alpha 2, recounted these events to the NSW Coroner's Court on Wednesday. The evidence came as the family of killed hostage Katrina Dawson indicated through their lawyer their view that police should have entered the cafe in an earlier, surprise assault.

Alpha 2 said he had been resting his 17 kilogram shield on some milk crates in the early hours of December 16, 2014. About 2am his tactical operations team on Phillip Street became aware of movement within the cafe.

Alpha 2 kicked the crates away and stood ready. A group of hostages burst out onto Phillip Street. He heard a shot from within the building, the first of the siege.

"Mate, we've got to go, we've got to go," Alpha 2 recalled saying to a fellow officer.

He said someone in his team raised the possibility the loud sound had been a slamming door.

"It's not a f---ing door slamming, it's a shot being fired," Alpha 2 said he replied.

Approval to enter the stronghold would not be given until 10 minutes later after Monis shot cafe manager Tori Johnson in the head.

Alpha 2 in his statement had said he was like "Usain Bolt" sprinting down to the main Martin Place entrance. Another officer fired a shotgun to break through the glass doors.

Then Alpha 2 became the first tactical operations unit member to enter, armed only with a Glock pistol. Monis would be dead in milliseconds.

Alpha 2 said visibility through the Perspex panel in his shield "wasn't the best" so he looked over the top of it. Across the cafe he saw the same figure he had seen hours earlier, peering through a Phillip Street window.

"I remember IDing him and going 'There's the c---, there's the c---, shoot him,' " Alpha 2 told the inquest. But the identification could not be relayed by radio. Alpha 2's radio had "shit itself" at the start of the siege, more than 14 hours before, and there were no spares, he said.

He had relied on "buddy comms" - relayed messages - with his colleague Officer A, who was directly behind him during the storming of the cafe.

He said he saw Officer A's laser sight travel up Monis' body.

"I watched his head explode and he fell down," Alpha 2 said.

Officer A fired 17 rounds and an Officer B fired 5. Bullets from one of two rounds struck and killed Ms Dawson, who had been lying behind Monis.

Michael O'Connell, SC, appearing for Ms Dawson's family, asked Alpha 2 how fatigued he had been after waiting in position for about 16 hours, much of that in summer heat, wearing gear weighing 25 kilograms.

Alpha 2 said he had not been fatigued. This was despite having started work at 7am after finishing a job after midnight the night before.

Mr O'Connell said he would submit on the Dawsons' behalf that police should have entered the cafe earlier under a "deliberate action" plan, partly to avoid officer fatigue.

The inquest continues before Coroner Michael Barnes.