A 71-year-old man died weeks after he was brutally beaten by a 15-year-old boy outside a Manhattan pizzeria, police said Wednesday. 

Brad Boonshaft and the teen got into a “brief verbal encounter” outside a pizzeria on Eighth Avenue near West 25th Street in Chelsea just before 4 p.m. September 15, cops and police sources said. 

The boy then pummeled the senior in the head, knocking him unconscious, police said. 

He was rushed to Bellevue Hospital with a subdural hematoma, authorities said. 

Boonshaft died of his injuries at the hospital on Sunday, Oct. 30, authorities said. 

The teen suspect – whose name has not been released because of his age – was arrested soon after the initial incident, and charged with assault on a victim over 65, cops said. 

Boonshaft’s death has been ruled a homicide by the city medical examiner’s office.