A 42-year-old man is in hospital in critical condition, after he was stabbed by another passenger on a transit bus.

"Richmond RCMP responded to multiple 911 calls regarding incident on a Coast Mountain bus,” said Cpl. Dennis Hwang of Richmond RCMP.

Video on social media showed paramedics giving the victim CPR in the doorway of the vehicle.

The violence broke out just before 2 p.m. The bus pulled over across the street from the Aberdeen Canada Line station.

RCMP shutdown No.3 Road, Eastbound, near Cambie Road for several hours while they investigated. Officers seized the vehicle so they could collect forensic evidence. The investigation shutdown the nearby Domo Gas station for all of the afternoon and much of the evening.

"It's alleged that a physical altercation occurred between two passengers,” Hwang told CTV News.

Police are unsure what sparked the fight or if the pair knew each other.

"One passenger, a 42-year-old male from Richmond was transported to hospital by emergency medical personnel suffering from critical stab wounds,” explained Hwang.

A 22-year-old Richmond man was arrested. RCMP says it's glad so many witnesses used their phones to call for help, something that's stopped being the norm.

"What we're seeing is instead of making the call to police, people would rather film a situation and get that up quickly for page clicks or something else."

TransLink said the incident did not impact its service.

"Public safety is always kind of an issue on transit,” said Trevor Jansen, a transit user. “I think there's a lot of deterrents out there. I see the green jackets, I see some of the officers on the platforms, but I'm not sure what else they can do to stop something like that."

A number of passengers on board the bus left before police arrived. Investigators are asking those witnesses to come forward.