A 22-year-old man is in critical condition after being struck by a box truck in Pitt Meadows early Thursday morning – a terrible accident that was witnessed by his partner.

The accident happened around 2:30 a.m. on the Lougheed Highway near Harris Road, where the couple had been trying to catch a taxi.

Ridge Meadows RCMP said it appears the victim was jaywalking when the truck hit him.

"He was on the north side of Lougheed Highway, was attempting to cross over to the south side to catch a cab when he was struck by a five-ton truck," Sgt. Brenda Gresiuk said.

Two witnesses, Matt Burnett and Jeremy Scholing, told CTV News they heard a loud bang coming from the roadway. They ran over to find the victim unconscious with a Halloween mask on the ground beside him.

"He didn't seem to be breathing at first, but I think Jeremy was actually able to bring him back," Burnett said. "I helped wipe the blood of his face and took the shirt off my back."

The Good Samaritans helped the pedestrian's girlfriend, called 911 and performed CPR before paramedics arrived. They said the victim was breathing when he was taken to hospital.

Gresiuk told CTV News the bystanders' response was likely "instrumental in him surviving."

"I'd just like to thank them for taking the time to stop and do the right thing," she said.

The pedestrian, who is a Port Coquitlam resident, remains in hospital Thursday afternoon in critical condition.

The cause of the accident is still under investigation, but the truck driver remained at the scene and police said all parties are co-operating.

Authorities closed a stretch of the Lougheed Highway for several hours overnight as they gathered evidence at the scene, but the busy road has since been reopened.

With files from CTV Vancouver's Sheila Scott