Mayor Jaime Ylarde said the source, whom he declined to identify, told him that a municipal councilor had visited star witness Reynaldo Morete and was overheard as convincing the latter to name him as the mastermind.
"Paglabas mo dito, milyonaryo ka na (When you walk out of here, you will become a millionaire)," Ylarde quoted the councilor as reportedly saying.
Under the law, charges against a suspect who has turned star witness are dropped.
Ylarde said he is now seeking another meeting with his source to convince him to testify against the councilor.
The Department of Justice (DOJ) summoned Ylarde to attend the preliminary hearing the other day, but he failed to make it because he said he was sick.
Morete, who was among the three initially charged in the killing of Agustin, publisher-editor of the Starline Times Recorder, has tagged him as the mastermind.
Morete has been placed under the DOJs witness protection program, a source in the National Bureau of Investigation (NBI) said.
Ylarde said he sent his lawyer, Joel Discaller, to the preliminary investigation not only to inform the DOJ that he was sick, but also to seek an extension of the deadline for the submission of his counter-affidavit.
He said he was given seven days from last Monday to submit the affidavit.
"But I think the (period) is just too short. But I will answer all the accusations. With Gods mercy, I will overcome," he said.
Ylarde urged the police to track down the two other suspects in the Agustin killing who are still at large.
Morete, who was arrested in Cabanatuan City by National Bureau of Investigation agents a week after the Agustin murder, has implicated his cousin, Noli "Boyet" Morete, and one Emmanuel Alday as the principal suspects, saying he only acted as a lookout.
Senior Superintendent Perfecto Palad said Reynaldo Morete did not mention Ylarde in his initial statement.
Ylarde, however, said his lawyer informed him that Morete has issued a supplementary affidavit implicating him as the mastermind.