A 55-year-old Brooklyn man died after he was knocked out by a maniac at Penn Station Saturday night, according to police and sources.

The straphanger fell victim to the senseless violence after bumping into the suspect on the northbound C and E train platform at the 34th Street-Penn subway station just before 7 p.m., law enforcement sources told The Post.

A heated argument erupted between the pair and the suspect clobbered the victim in the face, the sources said.

The victim then stumbled around the platform for about five minutes before collapsing, while his attacker fled.

Police then found the victim unconscious and unresponsive at the station just before 7 p.m., cops said.

First responders attempted life-saving measures before the man was rushed to Lenox Hill Hospital, where he was pronounced dead.

The assailant remained in the wind early Saturday.