At least seven people, including three students and three teachers, were killed in a school shooting at a high school on the outskirts of Bangkok, Thailand, according to police. More than a dozen other people were injured in the attack.

The shooting took place at The Debsirin School in the Bang Kruai district of Nonthaburi province. Police identified the suspected gunman as a 14-year-old student. Emergency responders rushed to the scene as authorities secured the school and began investigating the incident.

Thai Prime Minister Anutin Charnvirakul described the shooting as a premeditated attack. He said the teenager had been under significant pressure and tension before carrying out the shooting.

According to the prime minister, the suspect first killed his grandparents, with whom he lived, before traveling to the school. Authorities said he then opened fire, killing students and teachers and injuring more than a dozen others.

Police said the suspect later died by suicide after the attack. Prime Minister Charnvirakul said the teenager still had more than 30 rounds of ammunition when he died, adding that the number of victims could have been higher if the shooting had continued.

Authorities said the suspect used his grandfather’s legally registered firearm to carry out the attack. The prime minister also said the teenager had posted a photo of the gun on his Instagram account following a festival before the shooting.

Police continue to investigate the circumstances surrounding the attack, including the events leading up to the shooting and the suspect’s actions before arriving at the school.

Prime Minister Charnvirakul expressed his condolences following the tragedy and described it as a deeply saddening incident.

“This is a saddening incident,” he said. “He intentionally came to school today to commit this unfortunate case.”

The school shooting has left families, students and teachers mourning the loss of those killed while others continue to receive treatment for their injuries. Authorities remain at the scene as the investigation continues.