Armed with two semi-automatic military rifles, a pump-action shotgun and more than 200 rounds of ammunition, 19-year-old Julian Knight went to one of Melbourne's busiest roads and started firing.

It has been 35 years since Knight killed seven people and injured 19 others in what is now known as the Hoddle Street massacre.

The failed army cadet downed 10 beers at a pub, celebrating his mother's birthday, before his lethal evening shooting spree and only surrendered once he ran out of ammunition.

Knight had no apparent reason for the mass killing on August 9, 1987, except that he was depressed about having to abandon his dream of an army career and his car was playing up.

What happened in Clifton Hill, just outside Melbourne's CBD, that night shocked the nation and even seasoned homicide detectives.

Retired detective senior constable Graham Kent told Adam Shand's Real Crime: Australian detectives podcast what it was like to investigate the shooting and interview Knight.

He shared the callous way Knight had described the event to detectives, much like he was debriefing from an army mission.

"He had prepared for this, he was accomplished with firearms, he had military training, albeit he failed, he took time to gather his weapons, gather the ammunition, and work out where he was going to go, being familiar with the neighbourhood with which he lived," Mr Kent told the podcast.

"He certainly caused a lot of carnage."

Mr Kent said while Knight was callous in his description and gloated about his actions, he wasn't "crazy".

"There's no mental illness. He was not mad, not even in the lay sense, but he was certainly not mad in a legal sense. However he had a personality disorder," he said.

Knight was jailed for life in 1988, with a minimum of 27 years' imprisonment.

He has been in jail ever since and in 2014 parliament passed retrospective laws to prevent his release unless he's on his deathbed or too frail to harm others.

In 2017, he fought those laws in the country's highest court and lost.

The Hoddle Street massacre victims:

* Vesna Markovsla, 24

* George Mitchell, 27

* Georgina Papaioannou, 21

* John Muscat, 26

* Dusan Flajnik, 53

* Tracey Skinner, 23

* Shane Stanton, 21

Australian Associated Press