Three students, including the attacker himself, were killed in a shooting at a high school in Aztec town of New Mexico, United States, on Thursday, Reuters reported. It is not yet clear whether the shooter was killed by the police or he shot himself.

Authorities have not released other details yet. They said they will conduct interviews to start their investigation.

The incident took place at 8 am, just after the first period started at Aztec High School. The police responded within a minute of getting the first calls and entered the school through a window and a door, AP reported.

Students hid inside closets, classrooms, teachers’ offices and under desks as the shooter began opened fire. The school of about 900 students was evacuated, and the families of the victims were informed, the New Mexico Police said.