A Washington, D.C., man who authorities say posted on social media in support of the mail bombing suspect last month was denied bail Friday after being arrested on gun charges.

Jeffrey Clark Jr., 30, who allegedly told investigators that he is a white nationalist, was taken into custody last week after two relatives told authorities he was increasingly agitated, law enforcement officials told The Washington Post.

Authorities said they found multiple guns in his home, as well as military equipment, and that he had made anti-Semitic threats online.

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U.S. District Judge Michael Harvey denied bail for Clark on Friday after agreeing with law enforcement that he could potentially pose a danger to the public. He cited Clark’s posts on social media, calling them “menacing” and saying “it does appear that in recent weeks, his anger has intensified,” according to the Post.

Clark allegedly posted on the social networking site Gab after the shooting last month at the Tree of Life Synagogue in Pittsburgh, “Get used to it libtards. This was a dry run for things to come.”

“This statement implies that Jeffery Clark did know more about the attack in the Tree-of-Life synagogue, and that there was more to come,” authorities wrote in a court filing.

However, Clark’s lawyer argued that the post was related to Cesar Sayoc Jr., the man accused of mailing explosive devices to prominent Democrats and former intelligence officials who have exchanged criticism with President Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE.

Sayoc on Thursday pleaded not guilty to all 30 charges against him in federal court in New York.

Prosecutors said at a detention hearing for Clark on Friday that they now believe he was referring to the arrest of Sayoc, BuzzFeed News reported.

Regardless, Harvey cited the posts and the weapons and equipment found in Clark’s home as evidence “that the defendant was preparing for something.”

Relatives told police that Clark and his brother were involved in the alt-right movement and became interested in guns in 2016 because they believed there would be a civil war. They also “fantasized about killing ‘Jews and blacks,’ ” according to the court filing.

Clark is charged with possessing a firearm while using or being addicted to illegal drugs and possessing a high-capacity ammunition clip.