PHILIP, S.D. (AP) — The South Dakota Highway Patrol is trying to determine why two pickup trucks collided northeast of Philip. KELO-TV reports that investigators say the trucks collided on a gravel road around 9:30 a.m. Sunday. A 50-year-old man was killed. A 12-year-old and a 59-year-old were taken to the hospital with serious injuries. Investigators say no one involved in the crash was wearing a seat belt.