KENNEWICK, Wash. – Mason Ashby, 15, was found guilty of attempted murder, threats to bomb or injure property and 11 counts of unlawful possession of a firearm on Friday afternoon. The verdict came after a four-day bench trial in juvenile court, according Eric Eisinger, Benton County Prosecuting Attorney.
The Kennewick Police Department (KPD) was first alerted on September 20, 2025, about a TikTok post that reportedly showed a planned attack on Kamiakin High School. The post had been reported to the FBI before KPD was notified.
The execution of a search warrant at Ashby’s grandparent’s house, where he lived, led to the seizure of more than 20 firearms. Authorities also found a color-coded map of Kamiakin High School with annotations like “peak students” and “could shoot through windows,” along with other documents referencing school shootings.
Police later uncovered a manifesto that Ashby created, intended to be discovered after his planned attack on the high school.
The Benton County Prosecutor’s Office thanked two individuals from Punta Gorda, Florida, who reported Ashby’s TikTok post to the FBI.
“The planned attack was avoided based on their call, and as such this case is the perfect example of how important it is to ‘see something, say something,’” Eisinger said.
A sentencing hearing for Ashby will be scheduled at a later date.
