Background: screengrab of the home where Justin Mohn is believed to have decapitated his father before displaying his head in a YouTube video. Inset: Justin Mohn (images via YouTube screengrabs/WPVI).
The next day, he shot his 68-year-old father, Michael Francis Mohn, in the head, before decapitating him with a knife and a machete — and posting a rambling YouTube video holding up the plastic ...