After a five-week trial, a jury found Michael Hari, 49, guilty on Wednesday of five federal charges related to the pipe bombing of the Dar al-Farooq Islamic Center in Bloomington, Minnesota, while worshipers were in the building for morning prayers, they said.
"This act of violence, driven by hatred and ignorance, shook our community,” US Attorney Erica MacDonald said in a statement.
The verdicts, she said, "represent a condemnation of that hatred and uphold our fundamental right to live and worship free from the threat of violence and discrimination."
US District Judge Donovan Frank has yet to schedule a sentencing date, but Hari faces a mandatory minimum 35 years in prison, prosecutors said.
Hari and two accomplices, all from Clarence, Illinois, about 35 miles (56 km) north of Champaign-Urbana, were arrested by FBI agents in March 2018.
All three were indicted the following June, but the other two, Michael McWhorter and Joe Morris, pleaded guilty to their roles in the bombing in January 2019.
Prosecutors described Hari as the ringleader who recruited the others into a terrorist militia group called "The White Rabbits" and drove a rented pickup truck more than 500 miles (805 km) on Aug. 4 and 5, 2017 to bomb the Islamic center.
After using a sledgehammer to break the window of the Imam’s office at 5 a.m. on Aug. 5, they threw a plastic container filled with a gasoline-diesel mixture into the building, followed by a 20-pound (9 kg) black powder pipe bomb with a lit fuse, prosecutors said.
The three men then drove back to Illinois, they said. The explosion damaged the Imam's office and the resulting fire caused extensive fire and smoke damage, they added.