A driver who witnessed a wrong-way police pursuit on Highway 401 moments before a fatal crash said he was hoping the chase would have been called off before lives were lost.

The pursuit began after a robbery near Green Road and Highway 2 in Bowmanville just before 8 p.m. on Monday. At some point the vehicle fleeing entered Highway 401 in the wrong direction, police said.

Around that time, Brodie Mills was driving to dinner, heading westbound on Highway 401 to Boston Pizza in Ajax, Ont. when he noticed a vehicle travelling westbound in the eastbound lanes, travelling at about 160 to 180 kilometres, he said.

There was at least two police vehicles “tailing” the suspect vehicle at the time, Mills added.

“They were crisscrossing traffic in and out. It was insane,” Mills told CTV News Toronto. “I was in the left lane doing 120 (km/h) with normal traffic and it was as if I was parked on the highway when they passed me.”

Mills told CTV News Toronto that the police vehicles pursuing the suspect were “keeping their distance on the shoulder” but were travelling at a high rate of speed.

A video, obtained by CTV News Toronto, shows a 17-second glimpse of the chase, which appears to have been captured from a dashcam on a vehicle headed eastbound on the highway.

At first, the video shows a standard highway of trucks and cars driving in the right direction. But then, headlights appear in the distance facing the driver, who quickly pulls to the shoulder of the road.

Moments after, a vehicle speeds in the wrong direction, followed by a police car close behind.

Highway 401 wrong-way crash

From about a kilometre away, Mills said he heard an explosion that he felt rock his truck, and later, he saw a van split into two pieces as he passed the scene of the collision while crawling along the highway for approximately three hours.

“I was hoping someone would have called it (the pursuit) off before it got to that point,” Mills said of the tragic ending which left four people dead, including an infant.

According to the Community Safety and Policing Act, which came into effect on April 1, police officers must determine that the risk to public safety of any police pursuit is outweighed by the threat posed by an individual fleeing in a motor vehicle that is not apprehended or identified before initiating a vehicle pursuit.

Police chase collision Hwy. 401

CTV Public Safety Analyst Chris Lewis said the police chase protocol is dependent on a range of factors, including the traffic volume and severity of the situation.

“Generally speaking, the officers that are in the chase can stop at any time they see fit,” Lewis told CP24 on Tuesday. “It's just awful no matter what, obviously, these officers have to live with this the rest of their lives.”

Durham Regional Police Service (DRPS) released a statement on Tuesday afternoon, acknowledging that "many questions" surround the incident. "However there is a legislated process regarding investigations conducted by the SIU (Special Investigations Unit) that our service must adhere to," DRPS said in the statement. 

"At this time our thoughts are with those impacted by this tragedy," they said. 

The SIU is looking into the circumstances surrounding the chase.