MANILA - A political ally of slain Calbayog City Mayor Ronald Aquino believes the mayor was killed by rogue members of the Philippine National Police.

"There are evidences, there are facts that can't be denied. So sad to note that the father of the city, of Calbayog was slain or murdered by rogue elements of the Philippine National Police," Samar 1st District Rep. Edgar Mary Sarmiento told ANC.

He also maintained the incident, where 6 people were killed including police officers, was an ambush. The PNP initially claimed it was a shootout that began after Aquino's group fired at the tailing police vehicle.

"I'm hoping that justice will be given to him. Again, this is a well-planned thing. For me, this is still an ambush," Sarmiento said.

It was the police who opened fire at Aquino's van while the mayor was on his way to attend his son's birthday celebration, he added. He said his information came from locals who witnessed the incident.

• 'Bakit naka-bonnet, M-203?' Calbayog mayor's slay an ambush, says lawmaker

The lawmaker has filed a resolution urging the committee on public order and safety in the House of Representatives to investigate the incident.

"In this case, how can people not judge what happened to our mayor? They were not in proper uniform. They were not in proper vehicles. Why do you have to clandestine your vehicles? Why do you have to wear bonnets, in this case? Why do you have to bring firearms, high-powered firearms at that, if the intention is just to inspect?" he said.

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Sarmiento also bared the incident was politically motivated.

"The people in Calbayog knows the reason behind this. This is about politics. There are rogue elements [of PNP] that allowed themselves to be used by politicians," he said.

However, he refused to disclose the name of the person who could have ordered the attack.

"I don't want to accuse anyone rather than to wait for the report from the National Bureau of Investigation what really happened to our mayor," he said.

Aquino was on his third and last term as local chief executive. In 2011, then Calbayog City Mayor Reynaldo "Ining" Uy was also killed by unknown assailants while attending a fiesta celebration in Hinabangan town.

• PNP nanindigang engkuwentro ang pamamaril sa Calbayog mayor; kampo ng alkalde umalma

The police have formed a special investigation task group to probe the incident that left 6 people dead, including Aquino.

The other fatalities were identified as Aquino's close-in security detail Police Senior Sgt. Rodio Sario; his driver Dennis Abayon; Police Capt. Joselito Tabada; Police Senior Sgt. Romeo Laoyon; and Clint John Paul Yauder, a civilian.

Sarmiento has also sought the help of NBI to conduct a parallel investigation of the incident.

• PNP: Slain Calbayog mayor not target of police operation

In an earlier interview with ANC, PNP spokesperson Brig. Gen. Ildebrandi Usana said Aquino was not a subject of a police operation.

He said members of Integrity Monitoring and Enforcement Group and Provincial Drug Enforcement Unit were to conduct a separate operation.

"They were there to conduct Red Teaming inspection on all police stations, incognito in fact, because they are actually monitoring performance of our police officers against illegal drugs, terrorism and some anti-crime operations," Usana said.