The first known school shooting occurred in a town in southern Estonia on Monday after a 15-year-old student reportedly shot and killed his teacher during class, according to The Associated Press.

The unidentified male student had reportedly made shocking posts on Facebook along with photographs of guns and war before he killed his 56-year-old female teacher, according to Estonia's leading Postimees newspaper.

"Don't judge me because I'm quiet. No one plans a murder out loud," Postimees quoted him as saying in an April 1 post, according to AFP.

The other post added "You inspire my inner serial killer."

The motives for the attack reportedly remain unclear. The student was taken into custody after the shooting. The teenager reportedly used a revolver registered to his father, police stated.

"The shooting took place during a German lesson and the teacher was fatally injured," police spokeswoman Kristina Kostina told AFP.

She continued, "There are no other victims or injured."

The high school principal reportedly described the boy as a "very well-behaved young man" who had previously had no trouble at school.

"His achievements in school were not bad, an average pupil," stated principal Aavo Palo, according to Estonian media.

Palo added, "I don't have any information that the teacher had any conflicts with students previously and up until now I have no idea what exactly happened in this case."

Shootings are reportedly uncommon in Estonia while people who are under 18-years-old are not allowed to possess weapons or ammunition.

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