A stranger stabbed another man in the head with a screwdriver on board a Bronx MTA bus Monday afternoon when he flew into a rage because the victim was playing drums on his lap, cops and law enforcement sources said.

The victim, 60, was tapping on his own legs while riding the bus at East Fordham Road and Marion Avenue in Fordham Heights around 2:10 p.m., according to authorities and sources.

That ticked off another man on board the bus — who suddenly stabbed him in the head without warning, the sources said.

The injured man was taken to St. Barnabas Hospital in stable condition, police said.

No arrests have been made.

This is a developing story