PINEDALE, Wyo. (AP) – One of two men accused of luring a woman and her four teenage daughters to a Utah house and tying them up in the basement surrendered to authorities in western Wyoming, while the manhunt for his son intensified.

Flint Wayne Harrison, 51, was arrested early Saturday at the Sublette County Sheriff’s Office and immediately began helping authorities seek his son Dereck James “DJ” Harrison, 22, who investigators believe is camping in the forested back country of Half Moon Lake. He is armed with two knives, possibly a rifle and a shotgun with high-capacity magazines, the sheriff’s office said.

Authorities urged campers to leave the area and residents to stay inside their homes.

The woman and her daughters are recovering after the Tuesday attack in Centerville, Utah.

The father and son had been using methamphetamine heavily over several days and falsely believed the woman had reported them to authorities, police said.

The younger Harrison was a close friend of the woman’s family. He often visited the home for dinner or picked the girls up from school. The teens, aged 13 to 18, had known him for several years.

The men are accused of tying the mother and daughters up with zip ties. When the elder Harrison hit the woman with a baseball bat, the teens began to break their ties and try to escape, according to charging documents. In the struggle that followed, one girl slapped away a shotgun pointed at her throat and another grabbed the bat and hit the son, police said.

The victims managed to escape.

The Harrisons fled and were eventually picked up by someone who took them to Salt Lake City, where they spent Tuesday night in a hotel.

The elder Harrison is a registered sex offender in Pinedale, Wyoming, where he surrendered for reasons still unknown to police. Investigators think the father and son had been in Wyoming since Thursday.

Authorities were using a state helicopter equipped with infrared technology to help with the search.

Both men are charged with 16 counts, including aggravated kidnapping and possession of a controlled substance.