A Middletown man has had his charges upgraded to involuntary manslaughter in the shooting death of his son last month in their apartment. The Bucks County District Attorney's Office said in a news release Wednesday that investigators determined Jorddan Thornton's 2-year-old son accessed a loaded firearm and shot himself in the head with it on Dec. 2. County detectives and Middletown police had been trying to determine how Thornton's son was shot since the incident occurred. Thornton is charged with involuntary manslaughter and endangering child welfare, both of which are felonies. Previously he had only been charged with endangering as the investigation continued.