MANILA - The Public Attorney's Office (PAO) said Thursday that 17-year-old Kian delos Santos was shot 3 times during an anti-drug operation, twice at point-blank range -- contrary to the findings of a police autopsy saying the teen was shot only twice and from a distance.

Delos Santos, whom police tagged as a drug courier, was killed in an alleged shootout with policemen in Caloocan last August 16. Witnesses however said Delos Santos was mauled by policemen, given a gun and told to run.

The Philippine National Police (PNP) Crime Laboratory on Wednesday said an autopsy they conducted showed the Grade 11 student was shot twice in the head. Police found no soot or stippling suggesting that Delos Santos was shot pointblank.

But Dr. Erwin Erfe, PAO's forensic laboratory director, said that Delos Santos sustained a third gunshot wound on his back, aside from those on the back and inside of his left ear, based on their independent autopsy.

Trajectory studies, Erfe said, also show the assailant shot Delos Santos in the back from a distance of about 2 feet before shooting him again pointblank in the ear twice.

"Nakita po naming mukhang may sunog iyung edge ng gunshot wound saka po yung skin sa loob ng tainga kaya ang ibig sabihin po noon, mukhang malapit ang baril sa tainga niya noong pinutok po ito," he said.

Erfe added that based on the angle of the entry wounds, the teen was already unconscious and sprawled on the ground when he was shot point-blank, suggesting there was no firefight.

"Kung nagkaroon po ng firefight, hindi po ganoon ang mapo-produce. Mahirap pa pong ma-produce ang ganoong acute angle na 5 degrees lang at saka iyung isa almost 30 degrees lang," he said.

"Mapo-produce lang po iyan kung ang biktima ay nakasubsob at ang gunman ay nasa paanan."

Each of Delos Santos' wounds was fatal, especially both head wounds which could cause immediate cardio-respiratory arrest, Erfe said.

PAO chief Atty. Persida Rueda-Acosta said her agency's autopsy findings prove that Delos Santos was intentionally killed.

"Kapag po kasi binaril kayo sa likurang bahagi ng katawan ninyo na hindi ninyo nakikita, iyung element of treachery, pasok dito e... Tapos iyung sa loob pa ng tainga, barilin ka. Napakagaling ng pulis; ang layo, napuntirya," she said in a separate DZMM interview.

"Hindi homicide lang iyun, papasok talaga ang elements of murder doon."

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The Senate is set to open its investigation on the teenager's death on Thursday afternoon. The National Bureau of Investigation, National Police Commission and Commission on Human Rights have also launched independent probes into the killing.