The sisters, 5-year-old Olivia, 8-year-old Evelyn and 9-year-old Paityn Decker, were found suffocated to death at an abandoned campsite in Washington state on Monday, police said, sparking an intense manhunt for their father, Travis Decker.

Travis Decker is a former member of the military who has enough wilderness survival skills to live in the woods on his own for weeks or months, the authorities said.