Families in Thailand are mourning nine victims, including a 12-year-old girl and five school staff members, after a 14-year-old boy opened fire at a school and allegedly killed his grandparents before taking his own life.

Fourteen people remain hospitalized, including seven in critical condition, with most of the wounded between 12 and 14 years old.

Officials said the gun used in the attack was legally registered to the boy’s grandfather, while reports indicated the teenager may have been experiencing school-related stress.

The school has suspended classes, as grieving families and community members gathered to pay respects and collect belongings left behind after the shooting, Al-Jazeera has reported.

Following the attack, Prime Minister Anutin Charnvirakul pledged to introduce stricter gun-control laws, including limiting the carrying of firearms in public to government officials on duty.