The Philippine National Bureau of Investigation (NBI) said Tuesday that the police killing of Albuera Mayor Rolando Espinosa in his jail cell was a “rubout” and said that it could be part of a much larger conspiracy.

Tuesday’s landmark ruling follows a Senate inquiry into the death of Espinosa—who had been publicly named on a “drug list” announced by President Rodrigo Duterte — and of Raul Yap, the inmate of the adjacent cell.

Both men were killed after a Criminal Investigation and Detection Group (CIDG) raided the jail and opened fire, ABS-CBN reports.

Despite the investigation’s outcome, in a speech on Wednesday Duterte insisted that the CIDG members involved would not serve jail time.

“I will not allow these guys to go to prison, even if the NBI says it was murder. After all, the NBI is under me, the Department of Justice,” he said in a mixture of Filipino and English.

“We mayors, congressmen, who do we believe – the police or a criminal?” Duterte added in Filipino.

Members of the raiding team had claimed that they shot Espinosa and Yap in self-defense when a gunfight broke out as they attempted to serve a search warrant. At the time, Duterte said he believed the police version of events.

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“It is patently clear that the acts of the CIDG-8 operatives showed a community of purpose or an implied conspiracy,” the NBI said in a statement, referring to the region number of the police team. “There was unison in their purpose and action, signifying that they were all moved by a single criminal intent.”

The NBI also said that it had filed multiple murder and perjury charges against 24 members of the CIDG team, including Superintendent Marvin Marcos, who Duterte recently said that he had reinstated as the head of CIDG-8.

Marcos had previously been sacked by the Philippine National Police for involvement with illegal drugs.

[ABS-CBN]

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Write to Joseph Hincks at joseph.hincks@time.com.