Murder and torture charges were filed Friday before the Department of Justice (DOJ) against four Caloocan City cops over the killing of 17-year-old Kian delos Santos last August 16.

Kian's parents, Saldy and Lorenza delos Santos, filed a complaint for murder against Caloocan City police station 7 chief Chief Inspector Amor Cerillo, PO3 Arnel Oares, PO1 Jerwin Cruz, and PO1 Jeremias Pereda. Oares, Cruz, and Pereda were also charged with torture (torture of a minor leading to death).

Several 'John Does' were included as respondents in the complaint.

Kian's parents were assisted by the Public Attorney's Office (PAO), led by its chief, Atty. Persida Acosta.

Complainants and their witness, "Choleng," personally subscribed to their affidavits in the presence of acting Prosecutor General Severino Gaña and State Prosecutor Tofel Austria.

Kian succumbed to three gunshot wounds; two in the head and one in his back. Policemen alleged he was a drug runner, but his parents insist he was not involved in the sale and distribution of illegal drugs and wanted to be a policeman.

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Police and PAO forensic experts said it was highly likely the teenager was already down on the ground when he was shot.

Kian's death has been met with wide public outrage, with Congress investigating the circumstances behind the controversial August 16 anti-drug operation.

PAO chief Acosta, meantime, bared her office is working to have the delos Santos couple and their witnesses admitted under the DOJ's Witness Protection Program (WPP).

Acosta is hoping the three witnesses to Kian's killing, now under the protective custody of the Senate, will soon be turned over to the PAO. However, Acosta is confident the case will stand in court even minus the testimony of the three witnesses.

In an ANC interview, Acosta said the complaint cited the affidavit of several witnesses, who earlier claimed that Kian was mauled by policemen and given a gun before he was shot dead. This was contrary to the officers' claim that the teenager was killed in a shootout.

"The elements of abuse of strength and treachery are present. This is cold-blooded murder because Kian has already knelt down when he was shot," she said.

"The second case is violation of the Anti-Torture Act... the elements of which are torture leading to death, torture involving a minor and torture inflicting physical, emotional and pyschological injuries to the minor.

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PAO, she added, has strong evidence that Delos Santos was the man being dragged by plain clothes police in a CCTV footage acquired by media.

Operatives had claimed that the man in the clip was a police asset.

Aside from the Senate, the DOJ, National Police Commission and Commission on Human Rights have also launched separate probes into the killing.

President Rodrigo Duterte said the police officers involved in the teenager's killing should be punished if found to have broken the law.

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Duterte said he had seen the CCTV footage acquired by media which showed plain clothes police dragging a man matching the description of Delos Santos, to a location where he was later found dead.