Nathaniel James McGuire, 20, has been federally charged with malicious damage to a building by means of an explosive, the complaint says.
Authorities said Wednesday's incident in Santa Maria appears to be isolated and the suspect has no known ties to terrorism.
McGuire was being held without bail. CNN is attempting to locate attorney information for him.
McGuire was arrested in July on suspicion of a firearms violation, during which deputies seized a loaded and concealed revolver that was in his pocket and was not registered, Santa Barbara County Undersheriff Craig Bonner said. McGuire was set to be arraigned for that case Wednesday, Bonner said.
Man threw explosive device inside Santa Maria courthouse on day of arraignment, officials say
McGuire on Wednesday threw a bag into the courthouse lobby that exploded, the complaint says.
"According to the on-scene bomb technician, the suspected improvised explosive device was a can containing a black powder with nails glued to the outside," the complaint says. "The device was wrapped in duct tape."
A deputy sheriff who witnessed the incident detained McGuire as he attempted to get into a car outside the courthouse, according to the complaint.
"McGuire yelled that the government had taken his guns and that everyone needed to fight, rise up, and rebel," according to the complaint.
Authorities searched the car and found "a shotgun, a lever action rifle, ammunition, a suspected explosive device, and 10 Molotov cocktails," the complaint says.
When interviewed by law enforcement, McGuire said he intended to kill the deputes working at the security desk upon his arrival and then retrieve a firearm from his car and kill a judge, the complaint says.
The FBI later searched McGuire's residence and found materials used to make explosives, it says.
CNN's Cheri Mossburgand Cindy Von Quednow contributed to this report.
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