ANKARA, Turkey — A former student opened fire at a high school in southeastern Turkey on Tuesday, wounding at least 16 people, before killing himself, an official said.

The 18-year-old attacker, armed with a shotgun, fired randomly inside a vocational high school in Siverek, Sanliurfa province. He later killed himself with the same shotgun after being “cornered by police,” Gov. Hasan Sildak said.

The attack left 10 students, four teachers, a canteen employee and a police officer hurt, Sildak said. While most of them were being treated in Siverek, five of the teachers and students were transferred to a hospital in the provincial capital because their conditions were more serious, the governor said.

The motive for the attack remains unclear. School shootings are rare in Turkey.

The attacker did not have a criminal record, Sildak said. The school had been declared safe and no permanent police officer was assigned to protect it, he added, calling the shooting an “isolated incident.”

NTV television and other media reports said the assailant had threatened an attack on the school on social media prior to the shooting.

One student told the state-run Anadolu Agency that he and a friend jumped out of their classroom window to flee the attacker.

“He suddenly entered the classroom and fired. He fired four or five times. Two people were hit. He then went into the next classroom,” Anadolu quoted Omer Furkan Sayar as saying. “We first threw ourselves to the ground and then two of us jumped out of the window.”

Sayar continued: “He didn’t say anything, he entered and started to shoot directly.”

Earlier, media reports said all students were evacuated and police special operations units were deployed after the assailant refused to surrender.

“The individual was cornered inside the building through police intervention and died after shooting himself,” Sildak told reporters, adding that a “comprehensive” investigation into the shooting would be carried out.

Video footage showed dozens of students running out of the school toward the gate and onto the street.