A Brooklyn man was taken into custody for attempting to spread Islamic State group propaganda and bomb-making instructions online.

FBI agents had been investigating Zachary Clark, 40, posing as Islamic State group sympathizers in encrypted chat rooms. Officials say Clark encouraged Islamic State group supporters to commit lone wolf attacks in New York City and even tried to teach them how to carry those attacks out.

Uncovered photos depict a truck labeled as the "ultimate mowing machine," seemingly referring to fatal attacks like one carried out two years ago in Manhattan in which eight people were killed. It was just one of the photos law enforcement says were shared by Clark in chat rooms where he was an administrator.

The criminal complaint added that Clark encouraged attacks inside of the transit system, and that he sometimes worked out of the Bronx, too. Officials say he shared PDF documents intended to teach supporters how to do things like "make a bomb in the kitchen of your mom."

From the Southern District of New York, where this case was filed, a representative tweeted, "Zachary Clark twice pledged allegiance to ISIS, and posted on encrypted pro-ISIS chat rooms numerous exhortations and instructions on bomb-making and other terrorist acts to be carried out in New York. Thanks to the Joint Terrorist Task Force, Clark now faces serious criminal charges for his alleged support of a terrorist organization bent on killing Americans."

Clark is expected to be arraigned in Downtown Manhattan and could face at least 20 years in prison.