Department of the Interior and Local Government Secretary Jonvic Remulla on Thursday said the Philippine National Police (PNP) is investigating the possible accountability of the parents and aunt of the two minors involved in the deadly school shooting in Tacloban City.

Remulla said authorities are looking into whether negligence by the adults allowed the 14- and 15-year-old suspects to gain access to the firearms used in the attack at San Jose National High School, which left three students dead and 20 others injured.

"Ang tinitingnan namin dito ay yung culpability ng tiyahin at ng magulang," Remulla said.

The PNP's initial investigation found that the 14-year-old suspect allegedly used a Glock 17 pistol owned by his aunt, a police officer assigned to Police Regional Office 8. The 15-year-old suspect allegedly carried a .38-caliber revolver registered to a security agency in Cebu.

Remulla stressed that firearm owners have the responsibility to properly secure their weapons to prevent minors and other unauthorized individuals from accessing them.

The PNP earlier said the police officer could face criminal charges for malversation under Article 217 of the Revised Penal Code, along with administrative sanctions for negligence. Meanwhile, the security agency that owned the revolver may face the revocation of its license to operate for allegedly failing to report the firearm as lost.

Remulla also said the PNP's initial investigation pointed to bullying as one of the factors that may have contributed to the attack. Authorities are likewise examining the influence of a violent video game on the suspects.

"Ang lumalabas sa initial feedback ay bullying gone wrong. Binu-bully daw 'yung dalawang estudyanteng 'yun at dahil doon ay na-influence sila sa video games," he said.

The investigation into the shooting remains ongoing.