DOYLESTOWN, Pa. — The man accused of decapitating his father in their home northeast of Philadelphia and posting a video of the severed head online first shot him with a gun he bought the previous day, the county prosecutor said Friday.

Bucks County District Attorney Jennifer Schorn said at news conference in Doylestown that Justin D. Mohn had a “clear mind” when he allegedly killed his father Tuesday before driving about two hours to a Pennsylvania National Guard training center where he was found with a handgun and arrested. An autopsy showed the man's father, Michael Mohn, had been shot in the head before he was decapitated with a knife and machete, she said.

Justin Mohn, 32, embraced violent anti-government rhetoric in writings he published online going back several years. He didn't have a history of being committed for mental illness and purchased the 9mm handgun legally, Schorn said, surrendering a medical marijuana card before the purchase so he could be eligible to buy the weapon.

“It was evident to us that he was of clear mind in his purpose and what he was doing, aside from what his beliefs are,” Schorn said.

A woman answering the phone at the Bucks County Office of the Public Defender said Friday that they were representing him and said the office declined further comment.

Middletown Township Police Chief Joe Bartorilla said Friday that Justin Mohn's former employer called police last year over concerns about his writings and asked for legal assistance with terminating his employment, which the police said his department couldn’t give.

Justin Mohn was arrested late Tuesday at Fort Indiantown Gap, where he was hoping “to mobilize the Pennsylvania National Guard to raise arms against the federal government," the prosecutor said. Schorn added that Mohn “wanted to speak to Gov. Shapiro to join forces." Gov. Josh Shapiro's office declined to comment.

The FBI's National Threat Operations Center got four tips about “concerning” social media posts Mohn made between 2018 and 2023, the bureau said. The FBI looked into each tip and found no evidence of anything illegal happening, and didn’t find Mohn to be an imminent threat.

“As there was no evidence of any ongoing illegal activities or indications of an imminent threat, it was determined that no further action could be taken,” the agency said.

Justin Mohn's mother discovered the remains of her husband in the Levittown home where the three lived together and went to a neighbor’s house to ask them to call police, Schorn said.

Justin Mohn’s video, which was taken down by YouTube after several hours, included rants about the government, a theme he also embraced in writings published online. Schorn said authorities took possession of the video but expressed concern over the hours that it remained online.

“It’s quite horrifying how many views we understand it had before it was taken down,” she said.

Michael Mohn worked as an engineer with the geoenvironmental section of the U.S. Army Corps of Engineers' Philadelphia District.

Justin Mohn faces charges of first-degree murder, abusing a corpse and possession of instruments of crime. He is being held without bail.

In the YouTube video, Justin Mohn picked up his father's head and identified him. Police said it appeared he was reading from a script as he encouraged violence against government officials and called his father a 20-year federal employee and a traitor. He also espoused a variety of conspiracy theories and rants about the Biden administration, immigration and the border, fiscal policy, urban crime and the war in Ukraine.

Police said Denice Mohn arrived at their home in the suburb of Levittown about 7 p.m. Tuesday and found her husband's body, but her son and a vehicle were missing. A machete and bloody rubber gloves were at the scene, according to a police affidavit.

In August 2020, Mohn wrote that people born in or after 1991 — his own birth year — should carry out a “bloody revolution.”

Mohn apparently drove his father’s car to Fort Indiantown Gap in central Pennsylvania and was arrested. Cellphone signals helped locate him, according to Angela Watson, communications director for the Pennsylvania Department of Military and Veterans Affairs.