Two people were treated at the scene and a third was being evaluated after a man set off fireworks outside 26 Federal Plaza in lower Manhattan on Monday morning.
Law enforcement sources said the man used a shopping cart loaded with fireworks, doused it with an accelerant and lit it, then menaced pedestrians with two airsoft rifles before being taken into custody.
The FBI said an individual set off an incendiary device outside the federal building, which houses a U.S. Immigration and Customs Enforcement field office.
The New York Joint Terrorism Task Force is now investigating the incident, which authorities linked to anti-ICE activism.