Vancouver police are working to determine whether an underlying medical condition contributed to a horrific SUV crash that killed two seniors and injured three others Monday.

The vehicle lost control near Seymour and Davie streets shortly after 5:30 p.m. then slammed into a tree, slipped onto its side and slid into a lamp post.

Police said the 68-year-old driver and his 70-year-old passenger were killed instantly, and three pedestrians suffered injuries ranging from cuts and bruises to a broken femur and punctured lung.

Const. Brian Montague said investigators are checking if a medical condition played a role in the crash, but evidence already gathered at the scene makes clear that speed was a factor.

“Speed is going to be a factor, there’s no question about that,” Montague said Monday.

Witnesses who live near the scene told CTV News they heard a loud bang, almost like an explosion, when the SUV crashed.

Holly Bligh said she saw the vehicle exit the Granville Bridge at a high rate of speed.

“This guy was just speeding ridiculously off the bridge, and ended up trying to cut off and rammed into the tree trunk and just flipped,” Bligh said.

Investigators have already gathered some surveillance video from the area but asked any witnesses who haven’t spoken with them to come forward.

Anyone with information on the accident can contact the Vancouver Police Department at 604-717-3012.