A Washington, D.C., man reported by his family for extremist behavior pleaded guilty to a federal gun charge on Tuesday, The Associated Press reports.

Jeffrey Clark Jr., 30, faces a maximum of 10 years in prison after pleading guilty to one count of illegal possession of firearms by a person who is an unlawful user of a controlled substance, according to the AP.

Clark was arrested on gun charges in November after authorities said they found multiple guns and military equipment in his home, and said Clark made anti-Semitic threats online. He was denied bail.

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Clark reportedly told investigators he is a white nationalist after he was taken into custody.

Clark's relatives notified authorities after he allegedly made anti-Semitic social media posts on the website Gab after the Tree of Life Synagogue shooting in Pittsburgh.

His relatives told police Clark and his brother were involved in the alt-right movement and became interested in guns in 2016, believing there were could be a civil war. Relatives said Clark "fantasized about killing ‘Jews and blacks,' " according to a court filing.

Clark allegedly posted on Gab after the Tree of Life shooting: "Get used to it libtards. This was a dry run for things to come.”

Authorities wrote in a court filing that the post implies Clark "did know more about the attack in the Tree-of-Life synagogue, and that there was more to come." However, Clark's lawyer argued the post was related to Cesar Sayoc Jr., who sent pipe bombs to Democrats across the nation.

Sayoc has since pleaded guilty to sending the explosives. His lawyers argued in a memo Tuesday that he became radicalized by President Trump Donald John TrumpSteele Dossier sub-source was subject of FBI counterintelligence probe Pelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Trump 'no longer angry' at Romney because of Supreme Court stance MORE's tweets and Fox News.