Blade-wielding maniac slashes teen on NYC subway in random a…

A maniac slashed a teen boy on a Bronx subway — as terrifying surveillance footage captured him stalking the platform while holding a giant blade after the random attack. 

The stranger stormed up to the 16-year-old straphanger and began arguing before fighting the teen onboard a southbound 2 train as it rumbled toward the Prospect Avenue station in Melrose around 2 a.m. Tuesday, according to police. 

The enraged madman then suddenly left the train car and returned with a massive blade, police sources said. 

That’s when he allegedly slashed the unsuspecting youth in the back of the head before fleeing. 

Frightening video released by the NYPD Wednesday shows the suspect holding a large knife and pacing on the Prospect Avenue platform as the train leaves the station. 

The victim, meanwhile, was rushed to Harlem Hospital in stable condition, police said. 

His attacker has yet to be caught.