BANGOR — A Bangor man accused of killing his 49-year-old girlfriend has pleaded not guilty.

David Coon entered the plea Wednesday in Superior Court. He’s charged with murder in the death of Sherry Clifford, who died from asphyxiation and a neck injury.

A police affidavit indicates Coon told investigators that the two were on the floor in a tussle when he covered her mouth to prevent her from screaming. He says she was having breathing difficulties when he got up, so he dialed 911.

Police described it as a domestic violence homicide.