"What a f**king idiot."
In the original video, posted to Facebook, the driver said he was doing 100km/h and said he could only guess what speed the Porsche had been travelling when it passed him.
Victorian Police Commissioner Graham Ashton said this morning the Porsche driver, who had been pulled over by officers before 5pm last night for speeding, was handing himself into police.
There is no suggestion the witness from last night's crash is the person driving the same car on March 21.
EMOTIONAL TRIBUTE TO OFFICERS
The secretary of the Victorian Police Association has delivered an emotional tribute to the four police officers who were killed in Melbourne last night.
The constables died when the truck ploughed into them as they stood on the Eastern Freeway near the Chandler Highway at Kew about 5.40pm on Wednesday.
The group included a female senior constable, a male senior constable and two male constables, one of whom had only recently joined the force.
The driver of a Porsche who was pulled over and fled after the officers were killed has been urged to contact police investigating the incident.
Police Association Victoria secretary Wayne Gatt paid tribute to the officers on Today this morning.
"I think the police force is waking up feeling numb, the members, the men and women of Victoria Police challenged deeply by this," he said.
"We are hurting for the families that we know are obviously shocked and in immense pain overall."
He was asked what he would like to say to the killed officers.
"We are proud of you, you pulled on your uniform and you did your job. We are proud of you, your families will be proud of you and you will never, ever be forgotten."
Victoria Premier Daniel Andrews sent a message of support to the families of the four officers late on Wednesday night.
"Tonight, four police officers lost their lives in the line of duty. And tonight, somewhere in our city, four families' hearts are breaking," he said. "Our hearts are breaking with them.
"But one thing is already clear: Though we may not yet know their names - we will always call them heroes," he said.
Speaking at the scene on Wednesday night, Victoria Police Chief Commissioner Graham Ashton described the incident as very tragic.
Two of the officers had intercepted the Porsche, which had been speeding on the freeway, and called for backup when they decided to impound the vehicle, as another two officers arrived.
Soon after, the refrigerated truck ploughed into the officers.
The Porsche driver, who is believed to be uninjured, then fled the scene on foot and is still at large.
"I'd strongly suggest he gets himself down to the nearest police station to present himself to assist with these inquiries," the chief commissioner said.
The truck driver is believed to have had a "medical episode" and was taken to hospital under police guard.
Ashton said it was unclear whether he experienced the episode before or after the accident or exactly what unfolded.
The truck driver will be interviewed and undergo testing for the presence of alcohol or drugs in his system.
"We don't know at this stage what has caused him to drive that truck into our police members," Ashton said.
Gatt said the deaths have shocked its members across the state.
"These police officers were doing something that we do 10 times, 20 times, 30 times a shift - intercepting a motor vehicle on the side of the road, this is the bread and butter of policing," he told reporters.
"This isn't stuff that you go to do and expect to be killed doing. But each and every time a police officer does that for the next little while, they'll have this in the back of their minds, there's no doubt."
Police Minister Lisa Neville said the tragedy has hurt the whole community.
The freeway remained closed early on Thursday in both directions between Bulleen Rd and the Chandler Highway, and drivers were being told to find alternative routes.
