A 29-year-old Moroccan man was arrested Friday in an FBI sting operation near the U.S. Capitol while planning to detonate what police said he thought were live explosives.

Amine El Khalifi of Alexandria, Va., was taken into custody with an inoperable gun and inert explosives given to him by the FBI, according to a counterterrorism official.

Justice department spokesman Dean Boyd said the suspect was closely monitored by law enforcement, and the purported explosives were deactivated, so the public was not in danger.

The man had been under investigation for about a year, according to a counterterrorism official and a law enforcement official, both speaking on condition of anonymity to discuss an ongoing investigation. He had overstayed his visitor visa for years, the officials said. The FBI provided him with an inoperable gun and inert explosives, the counterterrorism official said.

The man changed his mind about his intended target several times but ultimately decided on the Capitol after canvassing the area a couple of times, the law enforcement official said. The man is not believed to be associated with al-Qaeda.

Two people briefed on the matter told The Associated Press he was not arrested on the Capitol grounds, and the FBI has had him under surveillance around the clock for several weeks. They spoke on a condition of anonymity because they were not authorized to speak publicly.