Justin Mohn has “been ranting and railing about the government for 10 years now and how they’re out to get him,” a childhood friend told NBC News.

The man accused of killing his father and displaying his decapitated head in a macabre YouTube video has long been obsessed with conspiracy theories, say those who knew him.

Justin Mohn, 32, was arrested on charges of first-degree murder and other counts after his father, Michael Mohn, was found beheaded in their family home in Middletown Township’s Levittown section Tuesday evening, court records show.

In a video that was removed by YouTube hours after it was posted Tuesday, the younger Mohn described his father as a federal employee of 20 years and referred to him as a traitor to his country. He also called for the death of all federal officials while allegedly displaying his father’s head.

“We’re all just in shock right now,” John Prickett, 68, who lives down the block from the Mohn residence, said Wednesday.