The driver of a Porsche involved in a crash that killed four police officers in Melbourne took graphic photos of the scene before fleeing, police said.

The 41-year-old, who is known to police, was pulled over after allegedly driving at about 140kph on the Eastern Freeway in Kew on Wednesday afternoon.

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He underwent a drug test which allegedly returned a positive result.

As police were impounding his vehicle, a truck, which was travelling at 100kph, came off the main lanes of the freeway and crashed into the group of four police officers, who were standing in the emergency lane.

Victoria Police Chief Commissioner Graham Ashton said good samaritans tried to render first aid but the officers died at the scene.

‘Graphic’ photos

It’s alleged the Porsche driver took some “graphic” photos before fleeing the scene on foot.

“As chief commissioner, to have four officers killed last night, from someone who has clearly been driving erratically on the freeway with an extensive criminal history – it disgusts me… and to leave the scene is a very low act,” Ashton told reporters on Thursday.

The photos were shared on Facebook and Ashton asked the public not to further circulate those images.

Four police officers were killed in the crash. Credit: AAP

Victoria Police is also speaking to Facebook to have the images removed, Ashton said.

The 41-year-old is expected to hand himself in to police on Thursday morning.

Ashton also revealed the truck driver, a Cranbourne man, had “blacked out” and had a medical episode immediately following the crash.

Police executed a warrant at his home and unknown items were seized.

Active investigation

“We’ve got a lot of information to go through over the next few days that’ll give us a very good picture of exactly what happened,” Ashton said.

Ashton added the deaths of the four officers was a tragic reminder of how dangerous the job of a police officer can be.

“It is a tragic day for Victoria police, as I said last night, a tragic day for the families of these officers and we feel very deeply for them,” he said.

Emergency services at the scene. Credit: DAVID CROSLING / AAPIMAGE

“The whole force is reeling this morning from what’s occurred last night.

“It’s an unprecedented event for us to lose so many officers in one event, in one terrible collision on the freeway.

“(The officers were) just doing their work, doing the job, doing a duty that is performed by officers many times a day.”

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Police are still working through a number of active leads and the freeway remains closed.

“This is a terrible tragedy made worse of course by the fact that our state is dealing with many other significant challenges at the moment,” Premier Daniel Andrews said.

“To live a life in the service of others is a deeply impressive thing.”

Anyone with dashcam footage of the scene is urged to contact Crimestoppers.