Story highlights Edgar Welch allegedly traveled to a DC pizzeria to "investigate" a false story about a child sex slavery ring

He is charged with interstate transportation of a firearm with intent to commit an offense

(CNN) The criminal case against the North Carolina man whom police say fired shots in a Washington pizzeria while investigating an online conspiracy theory escalated to federal district court Tuesday, as prosecutors revealed new details about Edgar Welch's alleged plans for an armed siege.

After reading a false story circulating online that the Comet Ping Pong restaurant in Northwest DC was harboring child sex slaves -- a conspiracy theory that came to be known as "Pizzagate" -- 28-year-old Welch allegedly traveled to the nation's capital armed with an assault rifle, a .38 caliber revolver, a loaded shotgun, and multiple rounds of ammunition in order to "investigate" these reports on his own and "rescue" the children, according to court documents.

Welch allegedly told police that "while he was in the restaurant, he searched for evidence of hidden rooms or tunnels, or child sex-trafficking of any kind" -- finding none after he attempted to force open a locked door with a butter knife and then climbed on furniture to peek into a closed-off room.

No one was injured in the nearly 30-minute ordeal, but prosecutors allege Welch fired his AR-15 multiple times inside the restaurant and pointed it at a Comet employee he encountered before surrendering to police.

The federal complaint provides a further glimpse into Welch's alleged activities in the days leading up to the incident on December 4, including his cell phone calls and text messages.

Read More