He was crossing the road at the corner of Elizabeth and Bourke streets and he can still hear the car, the screams, the thuds of people being hit and the sirens in the aftermath.

Mr Barry said he was on the way to the Australian Open.

"As I was just about to cross the road with a friend, we heard the sirens coming down Bourke Street Mall," he said. 

He said it was hard to understand exactly what was going on during the seconds the incident unfolded. 

"It was basically a matter of a few seconds, it was all over and all done, but the carnage was left afterwards," he said.

He said most of his life he had been a fuel tank driver and he had seen some "horrendous" incidents. 

Mr Barry said he had witnessed about five incidents in which people were killed. He said the death of 10-year-old Thalia Hakin in the Bourke Street case was traumatic because he had witnessed the death of a young girl about 20 years ago. 

"Because they were children, it's had a trigger effect on me," he said. 

Mr Gargasoulas, 29, was sentenced to life in prison on Friday with a non-parole period of 46 years. 

Mr Barry said he didn't believe the punishment was harsh enough and wanted the death penalty reintroduced. 

"I'm a firm believer that if you do the wrong thing, and it's proven, you should not be here," he said. "If you make the wrong choices and you kill people, and it's proven, you should not be here."