HILLSIDE – The investigation started months ago, when the FBI noticed an email message: A man in the Chicago suburbs was using an account to distribute chatter about violent jihad and the killing of Americans.

Two undercover agents reached out and began to talk to him online. In May, they introduced him to another agent who claimed to be a terrorist living in New York.

The operation ended Friday night, an affidavit describing it says, when the man was arrested and accused of trying to detonate what he believed was a car bomb outside of a Chicago bar. Prosecutors said an undercover agent gave Adel Daoud, a U.S. citizen from the Chicago suburb of Hillside, a phony car bomb and watched him press the trigger.