MANILA- Justice Secretary Vitaliano Aguirre II on Thursday hinted that witnesses who testified on alleged police abuse in the killing of 17-year-old Kian Loyd Delos Santos may have been "brainwashed."

At the Senate inquiry on Delos Santos' slay, Aguirre raised doubts on the credibility of two witnesses, both minors, who are currently under the custody of Sen. Risa Hontiveros, an opposition lawmaker.

"If these witnesses, especially they are children, 2 of them--13 and 16 years old-- are put under the custody of an individual especially if these individual’s fairness is in question, the credibility of these witnesses is bound to go down because we could never avoid the suspicion that they might have been brainwashed," Aguirre said.

The Aug. 16 shooting of Delos Santos, an 11th grader, has prompted public outrage amid evidence suggesting that the boy was executed.

CCTV footage showed police dragging Delos Santos to the spot where he was later shot dead. Witnesses also said that before the boy was killed, police gave him a gun and told him to run for his life.

An officer tagged in the teen's slay, however, denied that it was Delos Santos who was seen in the CCTV footage.

This despite earlier admissions by two other police officers that it was them captured on CCTV footage dragging Delos Santos on the night of the incident.

Hontiveros earlier defended her office's custody of the witnesses after Aguirre and Public Attorney's Office chief Persida Acosta pointed out that the senator has no power to take custody of the witnesses.

Aguirre and Acosta had said the witnesses should be placed under the Philippine National Police or the Department of Justice's (DOJ) Witness Protection Program (WPP).

"Ako lamang ay nagugulat sa biglang pangyayari. Mukhang may mga puwersang gumagalaw para kunin ang mga testigo, i-undermine ang kaso at limitahan ang accountability sa panig lamang ng mga pulis," Hontiveros said in an earlier statement.

• READ: Hontiveros defends custody of witnesses in Kian slay

She also dismissed the allegation of brainwashing, saying she is after the best interest of the witnesses who are minors.

"That is a serious allegation but this is not the main issue...I would like to insist always, isa po sa primary issue dito ay ang best interest of the child," Hontiveros said.

The senator earlier expressed willingness to transfer the custody of the witnesses should their families request so.

Aguirre, meanwhile, said the DOJ is open to extend WPP benefits to the witnesses and their families.

The justice chief had earlier decried public attention on Delos Santos' death, saying the case had been "blown out of proportion" by the media, social media users and other personalities.

• READ: Aguirre: 11th grader's death 'blown out of proportion'