"It sounds like the work of a disturbed mind, definitely. I'm glad he's in custody," Frauenfelder said.
TSA spokesman Ross Feinstein declined to comment, referring questions to law enforcement investigating the matter.
Onuoha, originally from Nigeria, had worked for TSA since 2006, FBI spokeswoman Laura Eimiller said. He showed up at LAX on Tuesday afternoon, resigned from his job and returned several hours later to leave a package at TSA's airport headquarters that was addressed to a manager.
A bomb squad found no explosives or harmful contents in the package but discovered an eight-page letter in which Onuoha expressed disdain for the U.S. and referenced the event that led to his suspension, Eimiller said.
Later Tuesday, a man believed to be Onuoha made two phone calls to TSA saying certain airport terminals should be evacuated, Eimiller said. During one call, the man told an employee he would "be watching" to see if authorities evacuated the terminals as instructed.
When police searched Onuoha's apartment in Inglewood, they found no dangerous materials but did turn up a handwritten note entitled "9/11/2013 THERE WILL BE FIRE! FEAR! FEAR! FEAR!" and containing unspecified threats that cited the anniversary of the terror attacks, authorities said.
An FBI affidavit says Onuoha told investigators he didn't mean the calls to the airport to be threats and he had no violent intentions. He said he wanted to start preaching in the streets beginning Wednesday, the anniversary of the 9/11 attacks.
Onuoha was arrested in Riverside, about 65 miles from his home. The church parking lot where his minivan was parked was cleared and a bomb squad robot conducted a search in and around the vehicle. Nothing dangerous was found.
Those who knew Onuoha saw no signs of any problems with him.
"There was never any indication of anything at all. Again, a big surprise," said Larry Vaughan, property manager at Onuoha's apartment complex.
Onuoha made his initial court appearance Wednesday, and his next court hearing was scheduled for Monday. Defense attorney Samuel Josephs declined to comment, saying he had not had time to review all the documents in the case.
AP Special Correspondent Linda Deutsch and AP writer Raquel Maria Dillon contributed to this report.
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