A 14-year-old boy from Washington was charged with attempted murder following a tip from Florida which led police to suspect he was planning a mass shooting.

Mason Bently-Ray Ashby, 14, appeared in juvenile court on Wednesday and pleaded not guilty to 13 charges, including attempted murder related to social media posts allegedly detailing plans for a “massacre” at Kamiakan High School in Kennewick, Washington. As reported by local CBS outlet KEPR, court documents reveal Ashby allegedly shared a color-coded map of the school on TikTok, featuring labels like “gear up,” “targets,” “potential targets,” “glass,” “be wary of,” and “exit.”

Someone from Florida reportedly saw the Sept. 19 TikTok post and alerted the FBI.

According to KEPR, the FBI alerted the Kennewick Police Department shortly after midnight on September 20, having traced the location of the poster. The police probe into cell phone data related to the post identified Ashby, a freshman at Kamiakan High School, as the suspect.

Police searched the family’s residence and discovered a hard copy of a similar color-coded map with additional notes such as “10:47 – 11:25 AM peak students” and “could shoot through windows.” Authorities confiscated Ashby’s phone and computer and allegedly recovered suspected drugs. Additionally, 24 guns, secured in safes, were also seized.

KEPR’s report claims police found video footage allegedly showing Ashby surveying the school, during which he purportedly mentioned shooting through the library’s windows. Furthermore, police allegedly uncovered various photos and videos depicting Ashby with at least 11 of the 24 guns located in his family’s home.

Police also came across a screenshot of a so-called manifesto that was allegedly attributed to Ashby. KEPR reported that it read as follows:

In a chilling message purportedly from Ashby, he taunted, “Hey, you found my manifesto. I’m sure you’ll all be laughing once you find out who I am and why I did what I did. Especially you people on WPD, I wonder if you’ll discover my accounts. I’m certain my Discord and other social media will be public almost immediately after the massacre. I’ve sent close friends photos of myself that will be deemed rare or unreleased by the time my plan is executed. Maybe I’ll even record the attack and share it with a select few.”

Ashby also allegedly involved one of his teenage friends, another 14-year-old who was arrested for illegal gun possession, tampering with evidence, and making a false statement to police. According to the Tri-City Herald, the police investigation uncovered a gathering to which Ashby allegedly brought a loaded Glock pistol, which had been reported missing by Ashby’s grandparents after his arrest.

Court documents stated that the other 14-year-old sent a text to the third boy at the gathering in which he discussed disposing of the Glock on Sept. 22, two days after Ashby was arrested. Police found the missing Glock at a local mall.

The other 14-year-old boy pleaded guilty to all three counts in juvenile court. He was sentenced to 40 days in juvenile detention, 12 months probation, and 25 hours of community service, and lost his right to own guns for the rest of his life.

At Ashby’s juvenile court appearance on Wednesday, Benton County District Attorney Eric Eisinger said that he cannot charge Ashby, who turns 15 years old this month, as an adult. Ashby was charged with attempted murder, 11 counts of second-degree possession of handguns, and a threat to harm property.