A 14-year-old student allegedly killed five teachers and staff members and his two grandparents before taking his own life in a school shooting north of Bangkok on Friday, in one of Thailand’s deadliest such attacks in recent years.

The teenager reportedly stormed Debsirin Nonthaburi School, where he was also a student, and opened fire using what police said was his grandfather’s handgun. More than 30 people were wounded in the attack.

Authorities initially reported that three teachers and three students had been killed, but Thailand’s Prime Minister Anutin Charnvirakul later revised the death toll, confirming five teachers and staff members had died.

The victims were identified as deputy head teacher Kittipong Somrat, math teacher Prapaporn Konsila, Thai language teacher Nantchanatporn Nakplang, guidance teacher Tiwaporn Wanich and secretary Saifon Sirikitchakajorn.

The school paid tribute to the five staff members, saying their “goodness and virtue” and “spirit as a teacher will remain in our memories forever.”

Police said the teenager also allegedly killed his grandmother and grandfather at their home, where he lived. His father told CNN he did not know why his son carried out the attack, saying the boy had a “good school result.” He also said his son was “guilty” but that he did not know why he allegedly carried out the attack.

Prime Minister Anutin said the suspect may have been experiencing stress related to his studies and warned that the attack could have been even worse, as the teenager still had more than 30 rounds of ammunition.

The suspect initially survived after shooting himself but was later confirmed dead. Emergency worker Kiatikhun Verapongpradith told Reuters that the teenager had shot himself in the right side of the head.

Students described scenes of panic inside the school, with some hiding under desks and others barricading classrooms with tables and chairs. Video verified by CNN showed students fleeing the school as staff helped them evacuate.

An unnamed rescue worker told Reuters that the scene was “total chaos” when emergency responders arrived. Students with wounds to their backs, chests and arms were treated at the scene.

The school has about 3,000 students and is located on a busy highway in the Bang Kruai district of Nonthaburi province.

Police said the suspect had searched for and viewed websites related to mass shootings before the attack. Authorities seized nine computers or electronic devices from his residence as part of the investigation.

The United Nations children's agency UNICEF said the suspect's young age raised “difficult questions” for society and called for improved mental health services for children and schools free from violence.

Thailand's Deputy Prime Minister Yodchanan Wongsawat said a new mental health action plan to support teachers and students would be announced following the shooting. The Ministry of Education also pledged to review school security procedures, particularly measures aimed at preventing weapons and other dangerous items from being brought onto school grounds.

The government announced financial compensation for victims and their families, including 20,000 Thai baht ($600) for each person killed and 5,000 baht ($150) for each injured person.

Police also recovered a handgun and multiple rounds of ammunition inside the school.

Thailand has relatively high civilian gun ownership compared with other countries in Southeast Asia. According to 2017 data from the Small Arms Survey, there were more than 10.3 million civilian-owned firearms in the country, equivalent to around 15 guns for every 100 people.

Gun ownership is legal in Thailand with a licence, although applicants must meet certain requirements, including being at least 20 years old and having no serious criminal record.