President Ferdinand Marcos Jr. on Monday ordered a thorough investigation into the shooting incident at San Jose National High School in Tacloban City that left three students dead and several others injured.

The directive was relayed by the Presidential Communications Office (PCO), which said the President also ordered authorities to strengthen security measures, particularly in schools.

"Iniuutos ang malalimang pag-iimbestiga rito at pinapasiguro ang proteksyon at kaligtasan sa lahat ng lugar, opisina, establisyimento, lalong-lalo na sa mga paaralan," the President's order stated.

The PCO said Marcos expressed sadness over the incident and extended sympathy to the victims and their families.

"Ikinakalungkot ng Pangulo ang pangyayari. Kahit sino pa man, lalo na ang mga magulang ng mga nabiktima ay makakaramdam ng lungkot at takot," the PCO said.

The Philippine National Police has already launched an in-depth investigation into the attack while exploring additional security measures aimed at protecting students and teachers nationwide.

Police Regional Office 8 director Brig. Gen. Jason Capoy said authorities are validating reports that one of the minor suspects may have been subjected to bullying since Grade 7.

Investigators are also examining how the suspects obtained the firearms used in the attack and how the weapons were brought inside the school premises.

The shooting has prompted calls for a review of school security protocols as authorities seek to prevent similar incidents from occurring in other educational institutions across the country.