MANILA - The Quezon City Police District confirmed that the suspect in the shooting incident in Ateneo de Manila University on Sunday is a doctor.

This was confirmed by QCPD director Police BGen. Remus Medina. He said that the suspect, 38-year-old Chao-Tiao Yumol, entered the venue inside a transport network vehicle service (TNVS) car.

Authorities are now looking into the security measures Ateneo implemented during its supposed graduation ceremony.

"Nag-rent ang suspek ng Grab at diretso lang sa loob at hindi na-check ang dalang baril. Titingnan din natin bakit nakapasok" he said.

Yumol also did not have an address in Metro Manila and would often change residences or even sleep in vehicles, Medina said.

“Mukhang determined assassin lumalabas itong si Dr. Yumol,” Medina said.

Yumol was able to leave the campus after he shot former Lamitan Mayor Rose Furigay, but he was apprehended by some residents, Medina said.

In a video circulating in social media, Yumol was seen pinned to the ground after he was arrested by the police.

Medina said those in the video where members of the QCPD Criminal Investigation and Detection Unit.

"Tumakas siya gamit ibang sasakyan na nasa university tapos naharang siya ng mga tao sa labas," he added.

Two guns were recovered from Yumol.

Based on investigation, the Furigay family filed 76 libel cases against Yumol after he accused the family of being involved in the illegal drug trade.

Authorities are now looking at this angle as a motive behind the crime.

"May kasong cyberlibel at tinitingnan din ang ilang personal na alitan," Medina said.

Speaking to the media after his arrest, Yumol insisted that the Furigays are drug lords. He also said the current administration should revive the war on drugs in Mindanao.

"Sana magamit ninyo 'yung perang pinagkakitaan ninyo sa pagbebenta ng droga sa probinsiya namin, pagsira sa buhay ng mga kabataan sa Mindanao dahil sa pagbebenta ninyo ng droga," Yumol said.

• 3 dead in Ateneo de Manila University shooting, including former mayor from Basilan

The family's legal counsel belied this accusation.

"This all started when he was operating an infirmary clinic," lawyer Quirino Esguerra told ABS-CBN News.

"The Bangsamoro Autonomous Region in Muslim Mindanao (BARMM) issued a cease and desist order. Because Lamitan City is included in BARMM, it was [then] Mayor Rose Furigay who implemented it," he said.

• Suspect in killing of ex-mayor held grudge over closure of clinic: Furigay lawyer

Furigay and her staff Victor Capistrano died from the shooting, while the former Mayor’s daughter Hannah survived the incident.

Ateneo security guard Jeneven Bandiala was also killed in the incident.

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Yumol is currently under the custody of the Quezon City police.