TALLINN, Estonia (AP) — A 15-year-old student shot and killed his teacher during class Monday in a town in southern Estonia — the first known school shooting in the Baltic nation.

Four other students were in the classroom at Paalalinna School in the town of Viljandi, police spokeswoman Tuuli Harson said. She said the shooter was apprehended and no one else was injured in the early-afternoon attack at the school of 450 students.

Government officials said the victim was a 56-year-old female teacher of German. Police said they had no details about a possible motive.

The Postimees newspaper reported that the shooter was a good student who had recently started posting pictures of guns and war on his Facebook account. The paper said one picture included text in English that read: "Don't judge me cause I'm quiet. No one plans a murder out loud." Another one said "You inspire my inner serial killer."

Estonian President Toomas Hendrik Ilves called the slaying a tragedy.

"It is not a tragedy of one school or one town; it is a tragedy for the whole of Estonia," Ilves said in a statement.

Estonian national broadcaster ERR reported that the boy is believed to have used a revolver. Police gave no details except to say the weapon was legal and registered to his father.

As a minor, the shooter faces up to 10 years in prison if found guilty of manslaughter.

Shootings are uncommon in Estonia. The country ranks 65th in firearms ownership, with an estimated 123,000 guns in civilian use among its 1.3 million people, according to The Small Arms Survey of 2007. Under 18-year-olds are not allowed to possess weapons or ammunition and handguns are not prevalent, although hunting weapons are common in rural areas.

In contrast, the United States has an average of 89 firearms per 100 people.