Several people, including three teachers and three students, were killed on Friday after a teenage gunman opened fire at his school on the outskirts of Bangkok, Thailand.

One 18-year-old student said he initially thought the gunshots were firecrackers going off, saying it “started getting more frequent, like ‘bang, bang, bang’ and then it went quiet at one point. And the shooting started again.”

The video below shows footage of students evacuating the building.

There is a “really sad atmosphere” at the Thai school where Friday’s deadly shooting occurred, as parents attempt to comfort their children amid the chaos, one parent said.

“My son heard his friend’s brother is in the hospital right now. He’s among the injured,” Karla Cripps, a CNN producer whose son attends the school but was not at the scene at the time of the shooting, said. “It’s been terrible for everyone.”