A man who drove the wrong way down Highway 99 over the weekend and crashed into two other vehicles is not expected to survive, according to police.

Another driver's dashboard camera recorded the 26-year-old going against traffic in a Volkswagen Golf on Sunday afternoon. The footage, which was uploaded to YouTube, shows several other drivers switching lanes to get out of his path.

Moments later, he was involved in a serious, multi-vehicle collision near the Highway 17 overpass in Delta that also put a 19-year-old woman in hospital.

Sgt. Lorne Lecker of the RCMP's Deas Island Traffic Services described the incident as highly unusual. In order to get onto the wrong side of the highway, the driver would have had to crash through a physical barrier in the closed counter-flow lane, Lecker said.

"We do have the occasional vehicle that comes onto the highway the wrong way. Usually that's either attributed to driver confusion (or) impairment," he told CTV News. "I can't see how this could be an oversight or a mistake."

But investigators have not determined why the Golf ended up on the wrong side of the highway. Lecker said if the driver does not survive his injuries, "we may never know."

"We have several theories that we're working on, but they are only that – theories," he said.

Investigators are also inspecting the vehicle and speaking with family members and witnesses.

Alarmed drivers originally reported the Golf might have driven the wrong way through the George Massey Tunnel, but police have since determined that didn't happen.

Instead, the driver came through the tunnel in the proper lane, then for whatever reason plowed through a barrier onto the counter-flow lane.

He eventually hit a Toyota RAV4 head-on then crashed with a Honda Pilot.

A young woman in the RAV4 was taken to an Intensive Care Unit with serious but non-life-threatening injuries. The RCMP said she has since left the ICU but remains in hospital in treatment.

A driver and passenger in the Pilot suffered minor injuries and were treated at the scene.

The crash closed part of the busy highway for several hours Sunday as crews worked to determine what happened and clear debris from the road.

Investigators are still trying to determine why the driver was travelling in the wrong direction. Anyone who witnessed the collision and hasn't spoken with police is asked to call Deas Island Traffic Services at 778-290-2400.

With files from CTV Vancouver's Shannon Paterson