Investigators said the victim, Edgardo Robles, 42, was on his way to Ormoc City from Manila when the gunmen, riding in two motorcycles, peppered his vehicle with bullets.
Robles sustained five gunshot wounds. He died while being rushed to the Calbayog District Hospital.
His assailants, police said, fled toward Gandara, Samar.
Police are investigating whether the ambush-slaying had something to do with the hotly contested fight between Locsin, who belongs to the Koalisyon ng Nagkakaisang Pilipino (KNP), and the camp of Lakas-CMD Rep. Eufrocino Codilla.
Codilla’s son Eric is challenging the re-electionist Locsin, while the mayor’s son Mitch is pitted against the elder Codilla in the congressional race.
The Philippine National Police has declared Ormoc an "area of immediate concern" in the May 10 elections.
Meanwhile, a policeman and a government militiaman were wounded in an ambush by New People’s Army (NPA) guerrillas in Barangay Baybay, Catarman, Northern Samar yesterday.
Senior Superintendent Pedro Desuasido, Northern Samar police director, said PO3 Romeo Brinzuela and CAFGU member Romeo Goco were on patrol when 10 rebels waylaid them.
The prompt arrival of military reinforcements prevented the insurgents from carting away the victims’ service firearms.
The military earlier confirmed that the NPA has intensified its attacks on police and military personnel in Leyte and Samar.