Story highlights Welch faces a mandatory minimum sentence of five years in prison on a local firearm possession charge

Welch will remain in jail while he awaits his next court appearance in early January

Washington (CNN) The North Carolina man whom police say fired an assault rifle in a Washington pizzeria while investigating an online conspiracy theory known as "Pizzagate" pleaded not guilty to all charges in federal court Friday.

Edgar Welch, 28, was indicted by a federal grand jury Thursday on federal and local gun charges, including a firearm possession charge that carries a mandatory minimum sentence of five years in prison.

Prosecutors allege he walked into the Comet Ping Pong restaurant in Northwest Washington and fired off multiple shots from his AR-15 while apparently in search of child sex slaves that he believed were being held at the restaurant. After Welch found no evidence child sex-trafficking, no one was harmed and he surrendered, according to court documents.

Welch's attorney, Dani Jahn, entered his formal plea of not guilty on all three charges, but conceded -- for now -- to her client's detention in jail pending trial.

Jahn also raised with Magistrate Judge G. Michael Harvey an "incident in which Mr. Welch was spoken to (by the media) without counsel" while in jail, and indicated that "protocols are now in place to make sure that that doesn't happen again." Welch gave an interview to The New York Times earlier this month, admitting his "intel" on the child sex ring at Comet "wasn't 100 percent."

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