“By all indications the male involved was quite distressed,” Mr Hill said.
He said police arrived at the scene following calls from the public to find the man visibly agitated.
“We tried to negotiate with the male, we tried to actually calm the male down. At a point during [the negotiations] the male has produced a knife and advanced on police members,” he said.
Police have been called to the man’s Narre Warren house previously, Mr Hill said, but he did not have a criminal record and had not been involved with police for some time.
Mr Hill said five police officers were involved in the initial exchange and seven others arrived at the scene as the shooting occurred. The entire incident was captured on the officers’ body-worn cameras and VicRoads freeway cameras.
One officer suffered minor injuries after falling to the ground as the incident ended.
“We’re still trying to understand why, what’s triggered this situation,” Mr Hill said.
“There would’ve been a number of passersby in motor vehicles that would’ve seen actually what occurred.
“It is a sad occasion.”
Homicide squad detectives will investigate the incident, under the oversight of the Professional Standards Command.
Police Association secretary Wayne Gatt said the union was providing support to the officers involved.
“Our understanding is that members have acted in self-defence, operating in an extremely dangerous environment,” Mr Gatt said.
City-bound lanes of the Monash Freeway are closed at Heatherton Road with motorists warned to expect major delays.
There is no access to city-bound lanes of the Monash Freeway from EastLink.
“Motorists should exit the inbound lanes of the Monash Freeway at their earliest convenience,” VicRoads said in a traffic alert.
“Belgrave-Hallam Road and the South Gippsland Freeway provide good options to exit the freeway.
“Motorists can then continue their journey towards the city using the Princes Highway.”
An SES tent has been set up in grassland between the city-bound lanes of the Monash and the EastLink on-ramp.
Anyone with information is urged to contact Crime Stoppers on 1800 333 000 or visit crimestoppersvic.com.au.
Anthony is a sports and general news reporter at The Age.
Erin covers crime for The Age. Most recently she was a police reporter at the Geelong Advertiser.
Simone is a crime reporter for The Age. Most recently she covered breaking news for The Age, and before that for The Australian in Melbourne.