Manila, Jan. 11 -- Philippine National Police (PNP) acting chief Lt. Gen. Jose Melencio Nartatez Jr. on Sunday ordered a thorough investigation into the Sibulan, Negros Oriental shooting that left four people dead, three of them police officers.

Nartatez ordered the Police Regional Office-Negros Island Region to conduct a thorough investigation into all circumstances surrounding the incident, saying there must be no cover-up, according to a press release.

At the same time, he directed all unit commanders to enforce stricter supervision and discipline among their personnel.

He emphasized that commanders at all levels are accountable for monitoring their men and must act decisively on any misconduct.

"Command responsibility applies at a...