Warning: Graphic content.

Bang Kruai District, Thailand: It was school work, a short study on secondhand trade, that got 15-year-old Wannapa out of class slightly early and down the elevators – to safety.

She didn’t know it then, but on the sixth floor of Debsirin Nonthaburi School’s building five, one floor below her own class, a 14-year-old boy was preparing for what in minutes would be Thailand’s worst mass killing since 2022.

The boy had come to his school, on the northwestern fringes of Bangkok, fresh from murdering his grandparents at their shared home earlier on Friday morning, a fact only discovered by police when they searched the place hours later.

By 10am, the second school period was almost over, and Wannapa was among a handful of students given permission to go downstairs and submit their finished work directly to their teacher’s office.

She was passing by the cafe with her friends, carrying her school work, when she heard the first pop from somewhere above.

“I didn’t think that much of it – I thought maybe someone was fixing something,” she told this masthead from her family’s shop, a few hundred metres from the school. The girl, who asked that her surname not be published, spoke with her parents’ blessing.

“Then I heard another four or five rounds. Students were like, ‘gunshots!’”

Wannapa and about 50 others fled into the school assembly hall, as they had been told to do in an emergency, barricading the doors with chairs and opening it only to let in students frantically knocking from the outside.

“I continued to hear gunshots – two or three more rounds – then I didn’t hear anything after that, but I might have been in shock,” she said.

The shopkeepers selling fried food about 15 metres from one of the school’s multistorey buildings heard the gunfire too. “I just thought they were dragging chairs or something,” one woman says. But then students started clambering out the upper floor windows and hiding on ledges by the outside air-conditioning compressors.

“That room where the window is open,” the woman says, pointing. “That’s where one of the teachers got shot.”

The mass school shooting, something more associated with America than the “Land of Smiles”, is the talk of the country and the neighbourhood. In a nearby 7/11 store, young staff members are overheard discussing how some of the students left their phones and wallets in the classroom and couldn’t get taxis home.

School shootings may be rare in Thailand, but gun ownership is not, and recent years have brought periodic, horrific killings, including the 2022 case of an ex-police officer who killed 36 people, including 24 kids, at a childcare centre in the nation’s north-east.

Prime Minister Anutin Charnvirakul has pledged to review gun laws. The events at Debsirin Nonthaburi School on Friday may be a catalyst for change.

The shooter had somehow got hold of his grandfather’s 9mm handgun, as he had done previously this year to show it off in an Instagram post.

For a time after killing his grandparents, the boy sat normally in class, investigators say, before suddenly pulling out the handgun and opening fire.

CCTV footage circulating on social media – confirmed by Wannapa as showing her school – captures a student exiting a classroom while still firing shots inside. Two people emerge into the hallway from the classroom next door, presumably to see what is happening. The boy appears to shoot at least one of them, before running down the hallway and out of frame.

Most of Wannapa’s classmates were still on the seventh floor. Many of them dashed down the stairway when the shooting began, and some evidently appeared in the shooter’s line of sight on the sixth floor. One was shot in the back. He was taken to hospital in a serious condition, and Wannapa says she heard that the wounded boy was going to survive.

On the fifth floor, below the initial volley of shots, 14-year-old Kwarchai and his classmates first thought someone was outside, shooting at birds. It soon became clear it was more serious.

“Everyone was shocked,” he says. “Some ran out of the classroom. Others hid under the tables.” Kwarchai chose the latter.

Wannapa and the others hunkered down in the assembly hall for 15 minutes or half an hour – she isn’t sure – until police arrived. It’s unclear whether the gunman had shot himself by this stage. Authorities say he turned the weapon on himself inside another building after police had made a cordon around its perimeter.

Left behind were five dead or dying staff members and close to 30 wounded, including students.

The shooter’s motive or mental state is unclear but the prime minister, Anutin, and investigators said the boy had been pressured by his grandparents over his school performance.

One of the shooter’s classmates arrived at Plai Bang police station on Saturday to provide a statement, and stopped briefly to field a handful of questions from reporters. He said he believed the shooter was hunting, unsuccessfully, a teacher who gave him a score of zero on an assignment.

Thai media, citing relatives, described him as a boy who kept to himself and spent most of his free time playing video games. Investigators say he had been searching online videos about mass shootings in the days before his attack.

Wannapa did not know him. But she knew three of the dead. They were her maths and Thai teachers, and a guidance counsellor.

“I feel so heavy on the inside,” she says. “I don’t know what to do.”

Lifeline 13 11 14. Beyond Blue 1300 22 4636.