Thai police investigating a school shooting outside Bangkok have said the 14-year-old suspected attacker had watched violent material online and previously brought an air gun to school, as the government prepared new safety measures.

Nine people died in the 7 August attack, including the boy. Police suspect he killed his grandparents at their home before travelling to Debsirin Nonthaburi School in Bang Kruai district, where he killed five employees and a 12-year-old pupil before shooting himself. More than 20 people were injured.

Atthapol Anusit, deputy commissioner of Provincial Police Region 1, said investigators found that the teenager had used social media to learn about firearms over a period of about one to two years.

“After examining the PC, it was found that the child had watched social media content involving violence,” Atthapol told reporters on Sunday.

He said police had found no evidence that the boy had trained or practised at a shooting range. Investigators have not established a single motive and are examining several possible factors, including family circumstances, school-related problems, disputes with other pupils and his online activity.

A teacher confiscated a BB gun that the boy had brought to school last year, police said. A knife was also found in his bag after Friday’s attack.

Officers have interviewed 17 witnesses and sent a firearm, cartridge cases, ammunition magazines, mobile phones and a personal computer for forensic examination.

Police previously said the handgun used in the attack belonged to the boy’s grandfather. The teenager had lived with his grandparents for about 12 years after his parents separated, according to investigators.

The death toll rose to nine on Saturday after a 12-year-old girl died from her injuries. The other people killed at the school were three teachers and two members of staff.

Thailand’s Education Ministry said it would develop new school safety protocols within three months. The proposed measures include mental-health screening, a referral system for people considered at risk, emergency-response drills, an anti-bullying campaign and improved checks to prevent prohibited items being brought into schools.

Prime Minister Anutin Charnvirakul has also said he will propose legislation restricting the public carrying of firearms.

The government said Mental Health Crisis Assessment and Treatment Teams had been deployed to provide psychological first aid and longer-term support to survivors, relatives, pupils, teachers and other people affected by the attack. Officials also urged the public not to circulate graphic footage or excessive details about the attacker.

Debsirin Nonthaburi School suspended classes for all pupils from 10 to 14 August, according to an official school notice.

The shooting was Thailand’s deadliest mass attack since 2022 and has renewed debate about firearm controls. Thailand has the largest estimated number of civilian-owned guns in Southeast Asia, according to figures cited by Reuters from the Small Arms Survey.

Police said the investigation remained open while forensic specialists examined the teenager’s electronic devices and other evidence.