Police have arrested the gunman they say fired into a crowd of spectators leaving a basketball game last week in Brooklyn.

Keenen Upson, 20, is charged with assault, criminal possession of a weapon and reckless endangerment for allegedly shooting five people in the rear schoolyard of Bishop Loughlin High School on Jan. 14.

Upson started spraying lead at about 10 p.m. on Vanderbilt and Greene avenues in Fort Greene, with bullets striking the victims, ages 17 to 19, in the arms and legs, police said. No one sustained a life-threatening injury. Another male, 18, was punched in the mouth during the melee.

Moments before violence broke out, Loughlin had lost the game to rival Christ the King.

“There was a great high-school basketball atmosphere in the gym, and, unfortunately, it had to end up with something like this,” Loughlin coach Ed Gonzalez said at the time.