TRENTON - A 3-year-old girl was killed in an accident involving a fire truck Friday night outside Sovereign Bank Arena, police said. While responding to a motor-vehicle accident, the fire truck collided with a pickup truck about 7:20 p.m. at Hamilton Avenue and Route 129, sending the pickup onto the median, where it hit the child, witnesses said. The fire truck knocked down a light pole, injuring several other pedestrians.