14-year-old accused in Kennewick school shooting plot cannot be tried as adult

The Kamiakin High freshman accused of plotting a shooting at his school in Kennewick will not be tried as an adult.

Mason Bently-Ray Ashby, 14, pleaded innocent Wednesday to a charge of attempted murder with a gun enhancement and 12 other charges in Benton County Juvenile Court.

Another Kamiakin student, Dylan Charles Carpenter, 14, pleaded guilty to three charges related to a gun missing from Ashby’s house.

Benton County Prosecutor Eric Eisinger told the Tri-City Herald on Wednesday that Ashby, who turns 15 this month, is too young to be charged as an adult for attempted murder.

Only someone that young with the most serious charges of first-degree or second-degree murder can be moved up to adult court.

The maximum juvenile court sentence for attempted murder that Ashby can receive, if convicted, would keep him incarcerated in a juvenile facility until he turns 21.

2 Kamiakin students arrested

Ashby was arrested at his home Sept. 20 after investigators seized guns, a map marked with “targets” at Kamiakin High, a manifesto and other evidence that appeared to indicate he was planning a shooting at his school.

An investigation started when a person in Florida alerted the Federal Bureau of Investigation late Sept. 19 of a suspicious short video posted to TikTok. It showed a map of Kamiakin High with areas labeled as targets and potential targets and what law enforcement believed was an indication that it was for a school shooting.

Kennewick police were able to trace the TikTok post to Ashby’s home and used a search warrant to seize 24 guns, plus other evidence that included a map similar to the one in the video and documents referring to shootings, according to court documents,

Investigators later would find a screenshot of the start of a manifesto discussing a “massacre” and describing how he had cracked the code to his grandfather’s gun safe at the house where Ashby lived, according to court documents. A video allegedly showed Ashby handling at least 11 of the guns.

The charges filed against him included 11 counts of second-degree possession of handguns and a threat to harm property.

Days after Ashby was arrested and taken to the Benton Franklin Juvenile Justice Center to be held in lieu of $1 million bail, his grandparents discovered that one handgun, which was not among those seized by law enforcement, was missing.

The investigation determined that Ashby had a loaded handgun when he was with two friends, one of them Carpenter, and that Carpenter had sent a text to the other friend about disposing of the gun on Sept. 22, two days after Ashby’s arrest, according to court documents.

Carpenter was arrested three days later on Sept. 23 and charged with illegal gun possession, tampering with evidence and making a false statement to police.

Kennewick boy pleads guilty

Both teens appeared Wednesday in juvenile court to enter pleas to the charges.

Carpenter, who had no prior offenses, pleaded guilty to all three charges. According to a court document, he twice told Kennewick police that he had no knowledge of the missing handgun.

But when police learned of a series of texts from Carpenter about tossing the gun away near Columbia Center mall in Kennewick, a search turned up the handgun, some of the ammunition and the magazine scattered near Quinault Avenue and Center Parkway.

Ana Segovia, a Benton County deputy prosecutor in the juvenile division, agreed with Carpenter’s attorney, Hayden Sebald, that Carpenter knew Ashby had a gun, but initially did not know of Ashby’s alleged plan for a school shooting.

Carpenter did not cooperate with police. His attorney said, “He was scared. Someone handed him a firearm.”

But the court commissioner said at some point Carpenter must have become aware of at least some of the alleged plot for a shooting at Kamiakin High. Yet he tried to destroy evidence and mislead police, Court Commissioner Darin Campbell said.

“Someone in Florida cared more about the safety of your school than you,” Campbell told Carpenter.

But Carpenter’s attorney argued that by the time Carpenter got rid of the gun, Ashby had already been arrested, thwarting the alleged shooting plan.

Campbell sentenced Carpenter to a total of 40 days in juvenile detention, 12 months probation and 25 hours of community service. Carpenter will lose his right to possess guns for the rest of life.

Campbell advised Carpenter to continue his education and in the future make friends who will not get him into trouble.

This story was originally published October 2, 2025 at 5:00 AM.