The man who fired a flare gun at a PG County emergency room last night has been arrested, the Post‘s Crime Scene blog reports. The man, who went to the hospital just after 7 p.m. last night, was arrested Monday morning at a local gas station, police said. He engaged staff members in an argument and proceeded to shoot a flare gun up in the air. No one was hurt in the incident and police declined to identify the man, though his wife told officers he had a history of mental instability.