The thug who allegedly started the subway brawl that led to the death of a Queens college student Friday was identified yesterday as a homeless man who spent time participating in the Occupy Wall Street protests, law-enforcement sources said.

Ryan Beauchamp, 33, — who allegedly attacked victim Joshua Basin, 20, at the Bedford Avenue station in a trendy section of Williamsburg — was busted last October for being in Central Park after hours while protesting with the anti-Wall Street group.

In last week’s subway brawl, both men fell onto the tracks, but Beauchamp was able to pull himself back onto the platform before the train crushed Basin.

Sources said a tipster fingered Beauchamp as the suspect after his sketch and image were released to the public.

A witness also picked his mugshot out of a photo array, sources added.