LEHIGH ACRES, Fla. (WFLA) — A 12-year-old student was arrested Thursday after authorities in Lee County said they found his written manifesto with plans to make bombs and plant them around his school.

The Lee County Sheriff’s Office said detectives were alerted to the student’s activities after his peers at Veterans Park Academy for the Arts saw him creating “concerning drawings.”

One of those drawings included a map of the school, depicting the exact spots where he would place bombs around the campus, according to officials. Investigators said the 12-year-old boy had also written a manifesto in which he “declared his intention to commit violent acts.”

A review of his school-issued Chromebook also revealed concerning search activity. Detectives said the teen had looked up bomb-making videos and researched notable serial killers and terrorists.

The 12-year-old was charged with written or electronic threats to conduct an act of terrorism and threats to throw, project, place or discharge any destructive device, the sheriff’s office said.

“I am beyond proud of the students who spoke up when they learned their peer had made violent plans,” said Lee County Sheriff Carmine Marceno. “The School Threat Enforcement Team began investigating immediately and uncovered disturbing renderings to carry out a violent act inside the school. LCSO detectives will continue to investigate and leave no stone unturned to ensure the safety of Lee County students.”

The investigation remained ongoing Thursday night, and no further details were immediately available.