An 18-year-old opened fire at a school Wednesday in Finland, killing at least eight. The shooter had posted a video on YouTube.

Tuusula, Finland ? Was it a massacre foretold on YouTube?

An 18-year-old gunman killed seven other students and the principal during a rampage through his high school in this quiet Finnish town – and investigators suspect he revealed plans for the carnage in Internet postings in which he urges revolution and grins after taking target practice.

Investigators said the gunman shot himself in the head after the shooting spree at Jokela High School in Tuusula, some 30 miles north of the capital, Helsinki. He died later at a hospital.

Authorities did not identify the killer. But fellow students and Finnish media identified him as Pekka-Eric Auvinen, a student in his final year at Jokela.

Witnesses described a scene of mayhem at the school in this leafy lakeside community, saying the shooter prowled the building looking for victims while shouting slogans for “revolution.”

Reacting immediately, the school’s principal issued orders on the loudspeaker for teachers to lock the doors to their classrooms. Some students tried to find safety by turning out the lights, while others leapt out of windows.

The teen killed five boys, two girls and the female principal with a .22-caliber pistol, police said. Authorities said one person was wounded by a bullet and about a dozen others suffered cuts and other injuries while fleeing the school.

Officials said more than 400 students ages 12 through 18 were enrolled at the school.

Police Chief Matti Tohkanen said the gunman didn’t have a previous criminal record. “He was from an ordinary family,” Tohkanen said. He said Auvinen belonged to a gun club and had gotten a license for the pistol Oct. 19.

Classmates said they had recently noticed changes in Auvinen’s personality. “He was a normal happy guy, a smart student who was very well informed about world events,” Tuomas Hulkkonen, a fellow student at the school, told MTV3 television news. “But recently, he started to get weird, and he withdrew into his shell.”

Gun ownership in Finland, a nation of hunters and sportsmen, is fairly common by European standards, but deadly shootings are rare. Finnish media reported that a school shooting in 1989 involved a 14-year-old boy who killed two other students apparently for teasing him.

Investigators trying to determine a motive for the attack were scrutinizing videos posted on the YouTube Web site Tuesday. The postings appeared to reveal plans for Wednesday’s deadly attack.

One video, titled “Jokela High School Massacre – 11/7/2007,” showed a picture of what appeared to be the Jokela school and two photos of a young man holding a handgun. Electronic music played in the background with a growling voice singing “I am your apocalypse.”

“I am prepared to fight and die for my cause,” wrote the person who posted the videos, identified by the username Sturmgeist89, or “storm spirit” in German. “I am a natural predator and will eliminate all those I see fit.”

Another video clip showed a young man clad in a dark jacket loading a clip into a handgun and firing several shots at an apple placed on the ground in a wooded area. He smiled and waved to the camera at the end of the clip.

A third clip showed photos of what appeared to be same man posing with a gun and wearing a T-shirt with the text “Humanity is overrated.”

The posting was later removed.

Finnish Prime Minister Matti Vanhanen described the bloodshed as “extremely tragic” and declared today a day of national mourning with flags to be flown half-staff.