An 18-year-old student from Idaho was arrested for planning to attack churchgoers in his hometown on behalf of ISIS, according to federal authorities.

Alexander Scott Mercurio, of Coeur d’Alene, Idaho, is accused of "attempting to provide material support and resources to ISIS" and pledging his allegiance to the terrorist organization, a Justice Department news release said.

In addition to supporting ISIS, Mercurio allegedly conspired to attack individuals at over 21 churches in Coeur d'Alene on Sunday with various weapons — including knives, guns and fire, according to the release.

Mercurio has been charged with "attempting to provide material support or resources to a designated foreign terrorist organization," the Justice Department said. He could receive a maximum penalty of 20 years in federal prison if convicted. 

Court filings on Tuesday show Mercurio is without legal counsel for his case.

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Alexander Mercurio intentionally planned to attack churches before the end of Ramadan, feds say

The FBI began looking into Mercurio when the 18-year-old reached out to "confidential human sources" online and revealed his support for ISIS and terrorist organizations, according to court documents filed in the District of Idaho. The confidential human source met Mercurio in person, and he again expressed his support for ISIS, the documents continued.

"Mercurio spread ISIS propaganda online and solicited ISIS's involvement in and approval of his propaganda efforts, discussed traveling from the U.S. to join ISIS, considered and planned ways to support ISIS financially, and most recently, set forth a plan to assault his father with a metal pipe, acquire his father's firearms and attack a local church," according to court records.

Mercurio's behavior "escalated" at the beginning of 2024 when he began planning a suicide attack on churches in Coeur d'Alene, the court records show. His plan involved using flame-covered weapons, explosives, knives, a machete, a pipe and firearms, according to the court records.

He chose a specific church and intentionally planned the attack to occur on April 7 because that meant it would happen before the end of Ramadan, court documents show.

FBI thwarts Alexander Meruciro's plan before he stole father's guns

The next part of Mercurio's plan involved incapacitating his father, restraining him with handcuffs and stealing his firearms to use for "maximum casualties in his attack," according to court documents. Before the attack, he bought butane canisters and a metal pipe, the documents continued.

While planning the attack, Mercurio made a "Bayʿah statement," which included him pledging his allegiance to ISIS and "stating his intention to die while killing others on behalf of ISIS," court records show. He transmitted the statement a day before he planned to carry out the attack, according to the court records.

Federal authorities managed to stop Mercurio before he could harm his father, court documents show. When they searched Mercurio's family's home Saturday, they found plans for the attack, the items he bought for the crimes and an ISIS flag in his bedroom, the documents continued.

Alexander Mercurio told the FBI's confidential source the attack plan, feds say

The FBI identified Mercurio as an online student at a local school who was issued a laptop and Wi-Fi Hotspot, court records show. Authorities found files on the school-issued laptop "confirming Mercurio's commitment to ISIS and its ideology," including photos of him using ISIS-related gestures and documents about socialism, communism and politics, according to the court records.

Mercurio also participated in an online group chat with other ISIS supporters, according to court documents.

"I'm 17 in USA," Mercurio wrote in the chat on Oct. 2, 2022, court documents show. "I know I try to keep secret, I'm in north Idaho very Christian and conservative parents are mad cause I'm not shaving beard and not letting pants go below ankle."

During an online conversation with the confidential human source, Meruciro told him the plan in detail, court records show.

"The plan is basically this: lie to my dad an say I'm going on a walk, leave, walk to a park, send the bayah video, delete all the social media on my phone (and) then walk to the nearest church," Mercurio wrote between March 25-26, according to court records. "Stop close by the church, equip the weapon(s) and storm the temple, kill as many as possible before they inevitably scatter, then burn the temple to the ground and flee the scene, then move onto the next church, rinse and repeat for all 21+ churches in the town until killed."

'This case should be an eye-opener', FBI agent says

U.S. Attorney Josh Hurwit said "we have no higher calling than to protect our nation and our communities from terrorism," according to the Justice Department's release.

“This case should be an eye-opener to the dangers of self-radicalization, which is a real threat to our communities,” Special Agent in Charge Shohini Sinha of the Salt Lake City FBI said in the release. “Protecting the American people from terrorism remains the FBI’s number one priority, and we continue to encourage the public to report anything suspicious to the FBI or your local law enforcement.”