State police say a Belfast woman was shot and killed Wednesday night. Lynn Day Arsenault, 55, was killed and her son, Matthew Day, 21, was injured, according to police. Police say Todd Gilday, 44, is charged with murder and could be facing more charges. Gilday was arrested Thursday morning at PenBay Medical Center in Rockport.State police say Gilday checked himself into the hospital early Thursday morning. His car was in the hospital parking lot around 7am. Gilday was taken to the Waldo County Jail in Belfast and is scheduled to be in court on Friday.