Online, he adopted the name of a Confederate cavalry leader dead for a century, hiding behind the persona to harass anti-fascists and further the goals of a white supremacist group, authorities said.

He cradled an AR-15 style rifle in a Facebook selfie and commented, “coming to a synagogue near you.” He posed with a knife in a post threatening Muslims, and shared an image saying women with romantic partners outside their race should “get the f---ing rope,” accompanied by a drawing of a hanging.

But away from his disturbing online presence, he was Fred C. Arena, a Salem County man who worked for a contractor at the Navy Yard in Philadelphia, according to the U.S. Attorney’s Office.

Arena was indicted late last month on charges that he lied to the FBI and on an application for a security clearance about his membership in Vanguard America, a white supremacist group that was seen at the 2017 “Unite the Right” rally in Charlottesville, Virginia.

At a hearing in Philadelphia on Wednesday, federal prosecutors argued that Arena was too much of a risk to be released pre-trial. In a motion with several attached screenshots from Arena’s social media, Assistant U.S. Attorney Joe LaBar wrote Arena’s family was unwilling to take him in, and he has lost his position at the Navy Yard.

A spokeswoman for the U.S. Attorney’s Office in Philadelphia confirmed Arena was held without bail Wednesday after the hearing, before Magistrate Judge David R. Strawbridge.

Authorities say Arena mainly posted online with the name John S. Mosby, who was a Confederate colonel also known as “The Gray Ghost,” whose unit would strike Union supply lines. Other times, he was “Big 88” or Fritz, occasionally with a racist middle name.

“He has expressed his desire to ‘get his hands on’ the witness he blames for focusing the attention of law enforcement on him," LaBar, the federal prosecutor, wrote. "He has boasted of his skills at using the anonymity of internet ‘trolling’ as a weapon against those he feels have wronged him. He has a well-documented access to firearms.”

Attorneys discussed whether Arena’s posts indicated an actual intent to commit harm. Prosecutors submitted several messages where Arena had bragged about breaking people who bothered him. At one point, he suspected an Antifa member of infiltrating a Vanguard group chat and claimed to have hired private investigators to “dox” members of the leftist group.

In messages, Arena - adopting the persona of a Confederate colonel - claims to have threatened someone in Charlottesville.Federal court documents

“Offensive is one thing, acting out is another,” Strawbridge said before ordering him held, according to a report in the Philadelphia Inquirer.

Arena, who was living in a hotel at the time he was arrested in October, had also threatened exes whom the FBI interviewed about the case, authorities said.

“He threatened to sever intimate parts of the women’s bodies and store the parts in a jar,” LaBar wrote. He threatened to cut another ex’s throat.

Brian Zeiger, Arena’s attorney, did not immediately respond to an email requesting comment Wednesday.

New Jersey Homeland Security officials said the Vanguard group claims about 200 members in 20 states, including New Jersey. The group has shown itself in the state before through recruitment fliers on college campuses including Rutgers and Princeton.

James Alex Fields, who is serving a life sentence plus 419 years for the murder of a protester in Charlottesville in 2017, was seen in photos with Vanguard members during the event.

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