The FBI has arrested a Michigan teen on suspicion of planning a mass shooting. 

Seann Pietila, 19, is accused of planning to commit a mass shooting at a synagogue, according to federal authorities.

FBI agents were in regular contact with Pietila online, where they claim he expressed interest in perpetuating a mass shooting at a Jewish temple before killing himself.

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Pietila note

A note found on the iPhone of Seann Patrick Pietila appears to specify the time, place and logistics of a planned mass shooting, according to the FBI. (FBI)

Federal authorities raided Pietila's house and found an extensive collection of weapons and ammunition.

"During the execution of the search warrant, investigators located the following items of evidence: .40 caliber pistol ammunition, .22 caliber ammunition, 12 gauge shotgun ammunition, a 12-gauge shotgun, a .22 caliber rifle, a Sig Sauer .40 caliber pistol (serial # 24B049058), .223 rifle magazines, an Apple iPhone 11, various knives and bladed instruments, scopes and firearms accessories, a camouflage tactical vest, a black tactical vest, black skull masks, a red and white Nazi flag, a ghillie suit, gas masks, and military sniper/survival manuals," an FBI report states. 

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The FBI also found a note written on Pietila's iPhone that appears to outline plans for a mass shooting, complete with a date and intended weaponry.

The teenager has been charged with transmitting an interstate threat to injure after the FBI obtained messages about his alleged plans. 

Pietila allegedly transmitted neo-Nazi-inspired rhetoric via Discord, Instagram and Pinterest.

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Pinterest Peitila nazi

Images from an FBI report show neo-Nazi posts collected by Peitila on social media app Pinterest. (FBI)

The alleged mass shooting was planned for March 15, 2024, in Pietila's phone, according to the FBI. 

That date would have been the five-year anniversary of a double mass shooting at Islamic houses of worship by New Zealand national Brenton Tarrant.

Norwegian national Anders Behring Breivik killed more than 70 people on the same date in 2011 at a youth camp. Pietila specifically mentioned Breivik in his messages, according to the FBI.