A 14-year-old boy from Washington state was charged with attempted murder after a tip from Florida led police to believe that he was allegedly planning a mass shooting.

Mason Bently-Ray Ashby, 14, made his first juvenile court appearance on Wednesday and pleaded innocent to 13 charges including attempted murder in connection to social media posts he made late last month in which he allegedly said he was planning a “massacre” at Kamiakan High School in Kennewick, Washington. According to court documents obtained by local CBS outlet KEPR, Ashby allegedly posted a color-coded map of the school on TikTok that included a legend with labels including “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.

KEPR reported that the FBI alerted the Kennewick Police Department after midnight on Sept. 20 after determining where the poster was located. The police investigation into the cell phone data connected with the post led authorities to Ashby, a freshman at Kamiakan High School.

Police conducted a search of the family”s home and allegedly recovered a hard copy of a similar color-coded map that included additional notations, such as “10:47 – 11:25 AM peak students” and “could shoot through windows.” Ashby’s phone and computer were confiscated, and police allegedly recovered suspected drugs from the scene. Also seized were 24 guns that had been locked in safes.

According to KEPR’s reporting, police found video of Ashby allegedly casing the school, during which he allegedly stated that he could shoot through the library’s windows. Police allegedly discovered several photos and videos of Ashby handling at least 11 of the 24 guns that were found inside 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:

Hey, you found my manifesto I am sure you will all be laughing at me by the time you figure out who I am and why I did what I did, especially you people on WPD I wonder if you’ll find my accounts haha, I’m sure my discord and other social media will be released nearly instantly after the massacre. I’ve sent close friends photos of me that will be considered rare or unreleased by the time my plan goes through, hell maybe I’ll even record the attack and send it to 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.