Idaho man arrested for planning attacks on churches in support of ISIS

The Justice Department on Monday announced the arrest of a man they say planned to carry out attacks on churches in Coeur d'Alene, Idaho, over the weekend after pledging support to the terror group ISIS.

Alexander Mercurio, 18, was arrested on Saturday on charges of attempting to provide material support to ISIS. Attorney General Merrick Garland and FBI Director Christopher Wray said in statement Monday that the FBI thwarted his plans to use knives, firearms and fire to carry out the attacks.

According to a criminal complaint unsealed Monday, the FBI's case against Mercurio started when confidential sources working with the bureau found him expressing support for ISIS online.

The bureau later arranged for an informant to meet with him in person -- and his conduct grew from pushing ISIS propaganda to allegedly planning to carry out a suicide attack on churches in Coeur d'Alene.

"His attack plan involved using flame-covered weapons, explosives, knives, a machete, a pipe, and ultimately firearms," according to charging documents. "His plan grew more precise as he eventually identified the specific church and date on which he planned to attack."

The plot allegedly crafted by Mercurio included plans to incapacitate his own father and restrain him so he could steal his guns "for maximum casualties in his attack."

Prosecutors say the day before his attack, on Saturday, Mercurio pledged his allegiance to ISIS and stated his intention to die while killing others on their behalf.

He was taken into custody before he could harm his father and acquire his guns, prosecutors say -- effectively thwarting his planned attack.

In a search of his house, law enforcement found "butane canisters, lighters, a pair of handcuffs, a knife, a pipe and a machete," according to charging documents. They also found an ISIS flag in Mercurio's bedroom.