The FBI arrested an Idaho teenager on April 6 for planning to attack churches in his hometown of Coeur d’Alene, Idaho, on behalf of the Islamic terrorist group (ISIS).

Breitbart News reports that the suspect, identified as Alexander Scott Mercurio, was taken into custody on Saturday as authorities with the FBI’s Joint Terrorism Task Force (JTTF) investigated the case.

Authorities say he was arrested the day before he allegedly planned to attack people in church services on Sunday. Mercurio reportedly planned to target twenty-one churches in his area on April 7 using weapons, including knives, firearms, and fire.

The suspect also gave a detailed plot of how he intended to carry out his mission. He said he would stop close to the church, equip the weapons, storm the temple and kill as many people as possible before they inevitably disperse/scatter

He also planned to burn the temple to the ground and flee the scene.

When officials arrested him at his residence, they discovered an ISIS flag, butane canisters, lighters, handcuffs, a knife, a pipe, a machete, and guns that belonged to his father.

He was also considering killing his father to gain access to his weapons.

Attorney General Merrick Garland released a statement on Monday announcing Mercurio’s arrest.

“The defendant swore an oath of loyalty to ISIS and planned to wage an attack in its name on churches in Coeur d’Alene, Idaho,” Garland said. “Thanks to the investigative efforts of the FBI, the defendant was taken into custody before he could act.”

However, the JTTF conducted the investigation and stopped his violent plot. Mercurio is in custody and awaits his initial appearance, which the Court will set.

If convicted of the alleged crime, Mercurio could face up to 20 years in federal prison. Reports claim that Mercurio has not yet had an opportunity to enter a plea. He is being held in a northern Idaho jail while he awaits his first court appearance, scheduled for late Wednesday morning.

In a press release on Monday, the U.S. Department of Justice Office of Public Affairs said the suspect was charged with attempting to provide material support or resources to a designated terrorist group.