Federal officials say they might have foiled a mass shooting in Austin this month, according to a criminal complaint filed Monday in U.S. Western District Court.

A confidential source told the FBI that Steven Thomas Boehle, 50, is a right-wing extremist who had planned the attack, according to the affidavit. The six-page filing does not give many specifics about the alleged plot, but does reveal that on April 12 Austin police seized three guns and about 1,100 rounds of ammunition from a North Austin residence where Boehle had been staying.

The document says the source told authorities Boehle "exhibits sovereign citizen extremism ideology."

BE THE FIRST TO KNOW: When big news breaks, we send Breaking News emails. Click to sign up

Boehle is charged with making a false statement in connection with the attempted acquisition of a firearm and unlawful possession of a firearm by a prohibited person. He is banned from purchasing firearms because of a 1993 misdemeanor assault conviction in Connecticut. The victim in that incident was an intimate partner of Boehle’s.

Boehle on three occasions had attempted to buy a firearm from an Austin-area retailer, according to the affidavit, but was denied each time. Boehle responded "no" each time to a question asking if he had ever been convicted of a misdemeanor crime of domestic violence. His most recent attempt came in December 2016 at Central Texas Gun Works on Ben White Boulevard.

A search warrant based on a narcotics investigation was executed April 12 at 615 W. St. John’s Avenue, the affidavit says. Police found the guns and ammunition in a closet along with some of Boehle’s belongings. A witness with whom Boehle was living became "visibly upset" when police told her about the guns. There is no mention in the affidavit about police finding drugs or why they had been investigating the location for narcotics.

STATESMAN IN-DEPTH: How a single improbable shot last year put a stop to a night of terror

It was unclear Monday where Boehle obtained the guns found at the address.

The home address listed for Boehle in the affidavit is an apartment in the 2300 block of La Casa Drive in South Austin.