An Iowa teenager was arrested Sunday on terrorism charges for posting photos of guns with a foreboding message about school on Snapchat.

The Federal Bureau of Investigation notified the Jefferson Police Department of the photo on Snapchat, according to the city's police log. It showed eight long guns with the message: "Ready for school 7 can join me."

Police traced the message to a 15-year-old boy in Jefferson. He quickly admitted to posting the photo, said Jefferson Police Captain Heath Enns. But it didn't appear that the teenager had any intention of taking the weapons to school, he said. 

"He was very forthcoming," Enns said. 

Police found eight firearms in his home: three BB guns; two single-shot, 12-gauge shotguns; a 50-caliber black powder rifle; a .22 rifle; and a 12-gauge pump shotgun. 

All eight firearms were removed from the home. 

Greene County Schools were notified about the incident, Enns said.

"But we took care of it pretty quickly," he said. "By the time we got to him, the case was already over."

The boy, whose name is not being released because of his status as a juvenile, was arrested Sunday afternoon. He faces a charge of threat of terrorism, a Class D felony, and a charge of 1st Degree Harassment, an aggravated misdemeanor. 

He is in the custody of the juvenile court system.

Juveniles in Iowa can face charges in adult court when facing charges of "forcible felonies." The names of juveniles tried in adult criminal court are released to the public. 

But Jefferson Police Chief Mark Clouse said Iowa code doesn't count terrorism charges among such charges. Forcible felonies include crimes of assault, murder, sexual abuse, robbery and burglary. 

"This is under the terrorism charge, not the assault language," the chief said. "If it's a forcible felony or an assault, then the juvenile's name is released. But it doesn't qualify in this case."