A Waterville man faces up to 15 years in prison after agreeing to a deal with federal prosecutors that would have him plead guilty to conspiring to provide material support to terrorists in a plot to attack a mosque in the Chicago area.

Xavier Pelkey, 19, and his attorney Christopher K. MacLean will change Pelkey’s plea to guilty at a hearing before Judge Lance Walker on April 7, according to the plea agreement filed Wednesday in U.S. District Court in Bangor. A second charge, possession of unregistered destructive devices, will be dismissed as part of the deal.

U.S. Attorney for the District of Maine Darcie N. McElwee and Assistant U.S. Attorney Craig M. Wolff would have prosecuted the case had it gone to trial. The government said Pelkey could face up to 15  years in prison, be required to pay a $250,000 fine, and be placed on lifetime supervision after his prison release if Judge Walker approves the agreement.

Pelkey was arrested Feb. 11, 2022, by FBI agents who found three homemade explosive devices in his Waterville apartment. The devices were made of fireworks bundled together with staples, pins and thumbtacks to create shrapnel, the FBI said.

Pelkey and his co-conspirators – two minors, including one in the Chicago area and the second in Canada – began plotting in November 2021 to conduct a mass shooting at a Shia mosque in the Chicago area sometime in March 2022, prosecutors said in court documents.

Pelkey and his accomplices were adherents of a radical Sunni Muslim group and believed that Shia Muslims were tantamount to non-believers and should therefore be targeted in violent attacks, according to the government. The three teenagers were also supporters of the foreign terrorist group Islamic State. Prosecutors said Pelkey and the Canadian minor intended to provide firearms, ammunition and explosives for the attack, including the three destructive devices found in his bedroom by FBI agents in February 2022.

If the case had gone to trial, federal prosecutors would have presented evidence that Pelkey and his co-conspirators planned to enter the mosque, separate the adult men from the women and children, and then kill all the adult men. They planned to travel to another Shia mosque or possibly another house of worship and do the same thing until law enforcement intervened. The three were prepared to die, according to prosecutors.

The three terrorists used Instagram to communicate about their plans to attack the mosque. In court documents, the underaged individuals from Chicago and Canada referred to Pelkey as “Abdullah,” a shortened version of Pelkey’s Instagram username, “Abdullah.ibn.ahmad.”