Senior Supt. Luisito Palmera, provincial police director, identified the two suspects as Froilan Legaspi of Barangay Sapsap and Ryan Armena, 19, alias Manok.
Legaspi voluntarily turned himself in to police authorities last Friday while Armena was arrested Sunday morning in his house where a handgrenade was found.
The two, however, named the mayors political rival as the brains behind the failed slay try.
Legaspi said they were paid P1 million by Marcelos rival, Antonio Romero, to carry out the assassination of the mayor and his brother, former councilor Rommel Marcelo.
Romero of the ruling Lakas-CMD lost to Marcelo in the 2001 polls. But Romero protested the outcome, accusing the mayor of massive cheating.
Last January, Marcelos house here was bombed. Several hours later, Romero was arrested in a checkpoint in possession of guns and ammunition. He was subsequently tagged with the bombing.
Also tagged in the assassination attempt were Roger Ramirez and one of Romeros sons. Ramirez was killed when the grenade he was holding exploded four meters away from him.
Marcelo was about to emerge from his house inside the Holy Cross College compound here to attend a fiesta in Barangay Rajal when he noticed Ramirez standing in front of the gate. He then ordered his two security escorts, PO2 Jonathan Reyes and PO1 Leonardo Santos to alight from the vehicle to confront the suspect.
When the two security escorts tried to accost Ramirez, he scampered away, triggering a chase. Two other suspects acting as lookouts also ran away.
When he was cornered, Ramirez lobbed the grenade at the lawmen who shot him in the stomach. He was hit by shrapnels from the grenade when it exploded.