TRENTON, N.J. — Gunmen opened fire at an all-night arts and music festival early Sunday morning, sending people running over each other in the scramble to safety, authorities said. One suspect was killed and 22 people, including two suspects, were injured. Of 17 people treated for gunshot wounds, four of them, including a 13-year-old boy, were critically injured but three had been upgraded to stable by evening, leaving only one man believed to be a suspect in critical condition, Mercer County Prosecutor Angelo Onofri. The shots rang out around 2:45 a.m.