The gunman who ambushed two Pennsylvania State Police troopers outside their barracks, killing one, used a rifle and might have had formal firearms training through the military or law enforcement, authorities said Monday. Releasing a profile of the killer, Lt. Col. George Bivens said investigators are focusing on the possibility that he had an "ongoing issue with law enforcement or the government" and was targeting the Blooming Grove barracks specifically. Authorities have been combing the dense forest surrounding the barracks and stopping motorists at checkpoints throughout the area to ask if they saw anything that could help lead to an arrest. Police continued to keep a tight lid on details about the ambush or the investigation, including the number of shots fired, where the shots originated and whether the troopers were able to return fire. A nonprofit group increased its reward offer to $75,000 for tips about the deadly assault at the remote post in the Pocono Mountains.