BOULDER, Colo. (AP) — A man in a wheelchair at a hospital who claimed his oxygen tank had a detonator was shot and injured by police after a four-hour standoff Monday.

Terrance Baughman, 32, was shot in the chest and was in critical condition after surgery, said Boulder Community Hospital spokesman Rich Sheehan.

It wasn't clear why Baughman was at the hospital in the first place. He had once been a patient there.

Baughman got out of the wheelchair during the standoff, leading officers to fire, police spokeswoman Sarah Huntley said.

"It was his movement that triggered the confrontation," Huntley said.

Police used a robot to remove a red bag found in Baughman's possession, and they took it to a nearby park and detonated it.