Six people were also wounded when the man opened fire with an M-16 rifle, he said.
"When we interviewed the wounded, they said they just woke to the sound of gunfire and that they were hit," Rey Enriquez, a nurse who treated casualties at a nearby hospital, told The Associated Press.
The killings came soon after robbers barged into a bank in the same province on Friday and killed 10 people by shooting them in the head, triggering nationwide outrage.
Avelino Razon, the national police chief, said on Sunday that his men were looking at the possible involvement of a known robbery gang in the bank slayings, but declined to give details.
A reward of 2 million pesos ($47,600) has been raised by the bank and private contributors for the capture of the bank robbers.