TUUSULA, Finland – An 18-year-old gunman opened fire at his high school in this placid town in southern Finland yesterday, killing seven other students and the principal before mortally wounding himself in a rampage that stunned a nation where gun crime is rare.

Police were analyzing YouTube postings that appeared to anticipate the massacre, including clips in which a young man calls for revolution and apparently prepares for the attack by test firing a semiautomatic handgun.

Investigators said the gunman, who was not identified, 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 Toolo Hospital in Helsinki.

The teen killed five boys, two girls and the female principal with a .22-caliber pistol, police said, adding that about a dozen more people were injured while fleeing the school. 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.”

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

Investigators were searching for connections to the shooter and a possible motive in YouTube postings that appeared to reveal plans for yesterday’s deadly attack.