WINNIPEG -- Manitoba's police watchdog is investigating after a man's back was bruised when Brandon police used a "less lethal" firearm during an arrest.

The incident happened on Jan. 18 around 11 p.m. in Brandon, Man., when officers received a call about a man in a home. Brandon police told the Independent Investigation Unit of Manitoba that when officers arrived a man threatened them with a knife.

Officers tried to get the man to surrender the knife, at which point he tried to escape and threw the weapon at a vehicle an officer was standing behind.

The IIU said officers than used a "less lethal" firearm, a weapon designed to stop a person without killing them. This caused a contusion - the medical term for a bruise- to the man's back.

He was taken into custody before officers took him to the Brandon Regional Health Centre where he was treated and released back into custody, the IIU said.

The IIU was notified of the incident on Monday.

Because the incident involves the discharge of a firearm that caused an injury, the IIU said this is a mandatory investigation.

Anyone who witnessed or has video footage of the incident is asked to contact the IIU toll free at 1.844.667.6060.

The IIU said the investigation is ongoing and no further details will be released at this time.