Authorities in Washington State said they have arrested a 13-year-old accused of obsessing over school shootings and living in a residence with an arsenal of firearms.

Sept. 9 (UPI) -- Authorities in Washington State said they have arrested a 13-year-old accused of obsessing over school shootings, threatening to kill others and living in a residence with an arsenal of firearms.

The juvenile was arrested at about 1 a.m. on Saturday by Pierce County deputies and SWAT members after receiving information about "a juvenile with school shooter ideations who was making threats to kill," the sheriff's office for Pierce County, which includes Tacoma, said in a statement.

Twenty-three firearms, some mounted on walls and accessible at all times, were discovered in the juvenile's home by deputies conducting a search warrant, it said, adding that other evidence found in the juvenile's bedroom indicated an "obsession with past school shooters."

The sheriff's office said they also found photos and writings in his room, showing the juvenile imitating similar behaviors of school shooters.

According to a press release from Saturday, loaded magazines discovered in the residence were etched with "school shooter writings." Police also found "clothing and writings that would support a typical mass shooting scenario."

"It appeared the suspect had everything ready to go to commit a mass shooting type of incident," the county sheriff's office said Monday.

"It is unknown who or what the intended target was going to be, but it's clear it was a matter of time before a tragic incident occurred."

The juvenile was not an active student in any school district and was last enrolled in the Franklin Pierce School District in 2021, the sheriff's office said.

Court documents obtained by ABC News states the juvenile has been charged with attempted threat to bomb/injure a school, unlawful possession of a firearm and unlawful possession of fireworks.