ELIZABETH, N.J. — Authorities say the alleged gunpoint robbery of a New York guardsman in New Jersey led to an exchange of gunfire, but no injuries were reported.The Union County prosecutor's office says Elizabeth police were called shortly after 1 a.m. Sunday and were told that the victim, a member of the New York Air National Guard Security Forces, was sitting in a parked vehicle when the suspect approached, opened the driver's side door and robbed him a gunpoint.