A man casually strolled on a Bronx street carrying a black assault rifle this week, disturbing new video shows.

The man walked on Webster Avenue in Olinville around 3:30 p.m. Thursday, carrying a black assault rifle with a high-capacity magazine, video released by the NYPD early Friday shows.

He never fired the weapon or pointed it at anyone, but caused “fear and alarm” among bystanders who spotted him, according to cops.

The suspect, last seen walking toward East Gun Hill Road, has a medium build and is about 6 feet tall, cops said.

He was last seen wearing a red hooded jacket, red sneakers and blue jeans.