Zameer Mohamed, 23, who once lived in the Los Angeles area, was taken into custody last Thursday as he crossed from Canada into Montana, the Los Angeles Times reported Wednesday.
Six days earlier, Mohamed allegedly made an anonymous call from a Calgary, Alberta, hotel to the Department of Homeland Security naming four people who planned to blow up a shopping mall this coming Thursday as part of an al-Qaida plot.
Mohamed told agents he wanted "retribution" against his girlfriend, a former co-worker at a Toronto bank who Mohamed said had stolen his paycheck, authorities said. The three others had declined his request to help him reclaim the funds, he told agents.
All four have since been investigated and determined to have no links to terror groups.
If convicted, Mohamed could face up to 10 years in prison.