Carolyn Kaster/AP Photo

Federal agents in Washington state have arrested an armed man accused of making threats against President Obama.

U.S. Secret Service agents and local law enforcement officers knocked on the door of Anton Caluori, 31, in Federal Way, Wash., on Tuesday afternoon, Secret Service spokesman Brian Leary said.

Caluori came to door with a shotgun, but was taken into custody without injury, Leary added, though Caluori made references to explosives, prompting a call to the bomb squad.

Secret Service Assistant Special Agent in Charge Bob Kierstead told local ABC News affiliate KOMO that suspicious items found in the man's apartment - potential explosive devices - prompted a sweep of the entire complex by a bomb squad. No bombs were found.

"He has a good education, he's a good boy, but he's done a stupid thing," Caluori's mother, Renee told KOMO. "I don't know a whole lot. How would you feel if your son got arrested? Never got arrested, was in the military, has a college education. And I'm just a little bit upset and shocked."

Obama, who was campaigning in Ohio at the time, did not appear to be in immediate danger.

"A threat against the president was delivered via email to a general FBI inbox," said Cathy Schrock with the Federal Way Police. "The Secret Service went down to investigate and the defendant was found to be armed when they arrived at the apartment."

Caluori is currently in federal custody and will have an initial court appearance Wednesday afternoon, sources said. He is accused of threats against the president and assaulting a federal officer.

ABC News' Chad Murray contributed to this report.