A mass casualty attack may have been prevented when federal authorities arrested a 22-year-old man from Burleson who idolized the Columbine High School shooters and had a homemade bomb, according to a news release from the U.S. Attorney’s Office for the Northern District of Texas.

Noah Robert Calderon was charged April 18 with possession of a destructive device and indicted on May 10, according to the Justice Department. His first appearance before U.S. Magistrate Judge Jeffrey L. Cureton was Monday.

Calderon “exhibited several indicators of potential violence,” including a fascination with mass shootings, weapons and white supremacy and a progression “from ideation to planning and preparation,” authorities said in a news release Tuesday.

“In apprehending Mr. Calderon, we may have averted a mass tragedy,” U.S. Attorney Leigha Simonton said in the release.

The FBI was alerted to SnapChat images where Calderon showed off homemade explosives, including one marked “SS,” which authorities believe to be a reference to the Nazi paramilitary group, according to the release. He also posted images of himself in tactical vests posing with long rifles and handguns and shared Columbine-themed memes.

The FBI in March received a tip that Calderon had detonated a homemade bomb in a neighborhood, including 911 calls about a loud blasting sound and smoke. After that, FBI agents reviewed Calderon’s Google account and found searches for mass shooters, how to make a pipe bomb and propane bombs and where the propane bombs were placed in Columbine, along with searches for the names of North Texas public schools.

He also bought 2 pounds of potassium perchlorate, 1 pound of aluminum powder and a fuse online, according to the release. When they searched his home on April 17, federal authorities found in the garage a brown shoe box containing items used to make and detonate a bomb, including a glass jar marked “frag” that was filled with metal BBs and lead. A white plastic container with 659.2 grams of explosive powder was found near the box.

A handwritten document labeled “Manifesto” found in Calderon’s room “glorified the Columbine shooters and espoused white supremacy,” federal authorities said.

“We are especially grateful to the tipster who alerted law enforcement to Mr. Calderon’s concerning social media posts,” Simonton said. “We encourage anyone who witnesses worrisome behavior to report it to law enforcement. Texas iWatch is anonymous and available 24/7.”

If he’s found guilty, Calderon could spend up to 10 years in federal prison.