A Massachusetts man has pleaded not guilty to charges he fatally shot his firefighter friend while playing with a handgun.

Patrick Riccardi-O'Connor was arraigned Wednesday in Woburn District Court on charges of involuntary manslaughter and related crimes.

Police found 24-year old firefighter David Atherton dead Tuesday night inside a Stoneham residence.

Police say Riccardi-O'Connor originally told them Atherton had shot himself but later admitted shooting Atherton while the two were drinking alcohol and "fooling around with the gun." Riccardi-O'Connor told police he didn't think the gun was loaded.

Prosecutors say the men were childhood friends.

Riccardi-O'Connor's attorney didn't immediately return a message seeking comment.

In a statement, Stoneham's interim town administrator recognized Atherton for his service as a town firefighter and National Guardsman.