Zameer Mohamed, 23, was charged Tuesday in federal court with a single felony count of using a telephone to maliciously make a false threat. He could face up to 10 years in prison if convicted.
Mohamed apparently was trying to get revenge on an ex-girlfriend, whom he falsely identified as part of the phony plot, because she bilked him out of money, the FBI said.
Mohamed, a citizen of Tanzania who lived in Canada, was being held in Montana and was to be taken soon to Los Angeles, FBI spokeswoman Laura Bosley said.
Authorities allege that on April 23, Mohamed called the Department of Homeland Security in Washington, calling himself "Al" and claiming to be a former associate of a terrorist cell linked with al Qaeda.
Two men and two women, he said, were going to enter the United States from Canada using false U.S. passports to "conduct an explosive attack on a mall in the vicinity" of the Federal Building in west Los Angeles, according to an FBI affidavit.
The man said he hoped that providing the information, including the names of the four people, "would enhance his chances of gaining U.S. citizenship," according to the affidavit.
The attack supposedly was to have occurred last Thursday. Police made the threat public and for several days increased patrols at shopping centers.
The FBI affidavit said Mohamed on Monday acknowledged making the call. "He identified the four individuals because they took money from him," the affidavit said.
They included his ex-girlfriend, a former co-worker at the Royal Bank in Toronto, the affidavit said. Mohamed said he had used the woman's bank account to direct-deposit his paycheck but she then refused to give him $4,000 in the account. He also named three of her friends.
Mohamed told the FBI that he was at a Calgary bus stop and saw a government poster with the number of a terrorist tip hot line "and had an idea to get back at her."
"Mohamed stated he never was a member of a terrorist organization and neither were these four individuals. He had picked Los Angeles as an alleged target randomly," the affidavit said.
He reportedly said he chose Los Angeles only because he was familiar with the Federal Building from an earlier trip to the UCLA law library. That specificity, however, is why authorities took the threat seriously, Los Angeles Police Chief William J. Bratton said a press conference Tuesday.
The investigation got underway after the original call to Homeland Security was traced to a calling card company that determined it came from a hotel in Calgary, the affidavit said.
Canadian police interviewed the desk clerk, who said a man later identified as Mohamed had stayed there from April 23-25 and provided a mobile telephone number as a contact, the affidavit said.