About 11:50 p.m. Monday, the 19-year-old gunman exited a green van and confronted a 23-year-old man in the 1100 block of North Keystone Avenue, a "hotbed" of narcotics transactions, police said. The assailant tried to shoot the victim but the weapon malfunctioned and during a subsequent struggle for the gun, the gun discharged and hit the victim in the shoulder, police said.