A Louisiana middle school student who stormed into a classroom Monday and fired a gunshot over a teacher's head, then shot himself in a bathroom had detailed plans for a rampage in a journal and suicide note, authorities said.

The 15-year-old student, whose name was not released, fired once around 9 a.m. local time inside a classroom at Larose-Cut Off Middle School, then shot himself in the head, said Lafourche Parish Sheriff Craig Webre. He was in critical but stable condition. The teacher had never taught the teen.

Webre said investigators found a note describing the boy's plans to "gear up" before his spree, along with a drawing of how he'd dress. Although he apparently was intent on killing people, he was armed with only four bullets for the .25-caliber, semiautomatic pistol he had taken from his father's home during the weekend. The boy's mother noticed he seemed nervous before school, but he said he was just worried about seeing his standardized test results, which were released Monday, Webre said.

About 500 sixth-, seventh- and eighth-graders attend the school in a rural community of about 7,000 people, some 45 miles southwest of New Orleans. Webre said the boy had no disciplinary problems at school and hadn't been in trouble with the law. The teen had no reason to be in the classroom, he said.

He was a year or two older than most of his classmates who described him as a quiet boy who never talked about guns or violence.

Webre said investigators found inside the boy's bookbag a completely filled journal and two loose sheets of paper that appeared to be a plan for the shooting and a suicide note. The school has both standing and handheld metal detectors, but they aren't used all the time and weren't in use Monday.

Webre said the boy arrived at the school in uniform — white shirt, khaki pants — but changed into camouflage pants shown in his drawing. In an expletive-laced note, he wrote, "First, I will tell my art class teacher that I had to go to the bathroom. Then I would go to the last stall and 'gear up."'

The school was scheduled to reopen Tuesday with enhanced security and several counselors on hand.