A 38-year-old Ohio man has been indicted on 28 charges including aiding the Islamic State, the Justice Department said Thursday.

Robert McCollum of Sheffield Lake, who now goes by Amir Said Rahman Al-Ghazi, was arrested last month while trying to buy an AK-47 from an undercover law enforcement agent. He allegedly pledged fealty to the Islamic State and its leader via social media last year, and has tried to recruit more acolytes for the terrorist group.

McCollum also allegedly wanted to launch an attack on U.S. soil. "He also expressed his own desire to perpetrate an attack on the United States and had attempted to purchase an AK-47 assault rifle," Justice said.

Beyond the "material support" of the Islamic State and firearms charges, the remaining 25 charges are related to his sale of marijuana over the last year and a half.

McCollum is the latest American charged with trying to help the Islamic State since the FBI announced it arrested an unprecedented number of would-be homegrown terrorists leading up to and since July 4.