MANILA, Philippines - Senator Ramon Bong Revilla Jr. on Monday filed a resolution directing the Senate to investigate the shooting incident in Atimonan, Quezon on January 6, where 13 people were killed.

In his resolution, Revilla pointed out the possibility that the incident was in fact not a shootout but a rubout. He cited latest reports showing that less than six of the 13 dead had guns, and information that the firearms found on the scene may have been planted.

"It is possible that there was no exchange of gunfire," he said.

The lawmaker also noted the initial findings of the National Bureau of Investigation (NBI) that contradict the reports and findings of the Philippine National Police (PNP).

He also said the Senate needs to know in its investigation, in aid of legislation, if authorities involved in the incident followed proper procedures.

"The sheer number of people dead in the incident ... makes an investigation imperative so that related legislations may be passed and/or amended as the need arises," Revilla said.

The resolution will likely be read on the floor and referred to the appropriate committee when session resumes on January 21.