Artemio Caguioa was preparing to go to the polls today when four young men suddenly approached him on the street in front of his house. A 52-year-old former military officer, Caguioa had returned to his home barrio, or neighborhood, to vote in today's presidential election. Instead, he became one of the first casualties.

At least two of the young men pumped eight bullets into Caguioa's body, neighbors said; then one of the gunmen fired a final shot into his head at close range. The four then calmly walked away, witnesses said. But who killed Caguioa and why remains a mystery. Was he the victim of election violence, or was he killed by Communist rebels to make him look like one?

Left at the scene was a campaign button for President Ferdinand Marcos and his running mate, Arturo Tolentino. In the sandy yard in front of his narrow, cement-walled house were torn-up sample ballots for opposition candidates Corazon Aquino and Salvador Laurel.

Valer Layug, a local opposition leader in Guagua, a town in Pampanga Province, north of Manila, said the victim had been one of his toughest organizers, a man who is "quite dangerous" because he was not afraid to take a stand. Layug suggested that the killing was carried out by militiamen loyal to Marcos to discourage people from going to the polls in this largely pro-opposition town.

However, other opposition sources insisted that electoral politics had nothing to do with the slaying. They indicated it was a "liquidation" carried out by hit men of the Communist New People's Army as revenge for a past misdeed, or as punishment for being a government informer. It was also possible, they said, that the killing had the secondary purpose of enforcing an election boycott promoted by the Communists and their leftist allies.

According to one account of the attack, the killers shouted, "Mabuhay KBL" ("Long live Marcos' New Society Movement"), immediately after the killing. Another version had them shouting, "Mabuhay NPA."

The case appeared to be a classic example of the confusion and contradictions that often make "election-related violence" in the Philippines difficult to sort out. It also exemplifies the fear such cases can arouse among Filipinos, who rarely testify against killers commonly called only "unidentified armed men."

"The people are deaf and blind," said Lt. Sonny Cunanan, the station commander of the Philippine Constabulary's detachment here charged with investigating the murder. He said he believed that Caguioa was the victim of a guerrilla killing possibly connected with his military background.

"They are getting stronger here," he said of the Communist rebels. "We cannot determine their strength, but what is happening now means they are gaining support from the populace."

The scene of the murder lies amid sugar and rice fields in this province that was one of the cradles of Philippine communism. Many walls are daubed with red paint promoting a boycott of the presidential election or denouncing the "U.S.-Marcos dictatorship."

Even more reticent than the witnesses, Caguioa's widow, professed to know nothing about the possible motives or identities of the killers. "I believe my husband has no enemy in this place," she said.