The victim, Romulo Guzman, 45, chief aide of defeated mayoralty candidate Eufrocino Codilla Jr., was shot in the back of the head with a caliber .45 pistol.
SPO4 Rudy Sano, who is handling the case, said Guzman was about to enter the dancing area when the gunman, in his twenties and wearing a black jacket and maong pants, shot him.
As Guzman lay bloodied, another man took his caliber .45 pistol and fled toward the shore, Sano said.
Witnesses said they earlier saw the two men at the tennis courts entrance apparently waiting for someone.
Guzman, according to his wife Annabel, survived an attack last July 1. He was in Codilla Jr.s house when one of three men aimed a gun at him but luckily, it jammed.
There have been a number of unsolved killings in the city, including the fatal shooting of a policeman inside a cockpit two weeks ago. Roberto Dejon