The victim, Elpidio Marcos Navaroza, 54, head of Barangay Bayambang, was walking home alone at a fishpond dike when the gunman blocked his path and fired at him several times.
Navaroza sustained gunshot wounds in the abdomen and nape.
Probers still have no clues on the motive behind the attack.
Navaroza had tipped off authorities about the presence of Chinese nationals here, leading to the seizure of steel barrels containing 425 kilos of shabu considered one of the biggest hauls in the country on Nov. 5, 1999.
Then President Joseph Es-trada even personally went to Lingayen town, the provincial capitol, to inspect the confiscated illegal drugs and gave Navaroza a huge cash reward.