The Ati-atihan religious festival in honour of Santo Nino, one of the most revered Roman Catholic icons in the Philippines, was stopped on Sunday, turning merrymaking into mourning for the victims.
"We are still investigating the motive for the violent shooting," said Edgardo Aglipay, the national police chief. "We are checking reports that this incident was drug-related, but we cannot discount other angles."
He said the provincial police chief was walking towards the municipal building after attending mass when a gunman opened fire at his group, sending hundreds scampering for safety.
The shooting began during a fireworks display to start the festival in Kalibo town, a gateway to the Boracay Island resort in central Philippines.
The festival commemorating the conversion of pagan natives to Catholicism in the 16th century is known for street dancing by people smeared with charcoal, wearing grass skirts and carrying wooden spears.