While arresting a belligerent passenger, a San Francisco BART transit officer and suspect bumped into a station window, causing shattered glass to rain down on the two men.
The arrest was captured on video by another passenger and posted to YouTube (see below).
The cop suffered a concussion during the arrest and was treated at a Bay Area hospital. A BART police commander said the officer's use of force would be investigated.
The suspect, Michael Joseph Gibson, was reportedly screaming racial slurs at other passengers and suffers from bi-polar disorder, according to a Daily News story.
Watch the arrest here: