A lone gunman in Collier, Pennsylvania, shot more than 10 people, killing four as well as himself, according a report in the Pittsburgh Post-Gazette. Witnesses say a man carrying a duffel bag entered L.A. Fitness, a chain gym, through the back door before opening fire. A woman in an aerobics class said the man entered the room and began shooting, prompting class participants to crouch and hide on the side of the room. Another woman, who was running on a treadmill at the time of the shooting, said she heard 12 to 15 individual shots. A man who was playing racquetball says he heard "about eight shots": "It was panic. Then we realized it was gunfire. Once the shooting started, everybody started running."