McStay Murders: Inside the Shocking Arrest of a Family Friend

Charles Merritt is arrested for McStay family murders

San Bernardino County Sheriff’s Department

By Elaine Aradillas

@elaineja

11/13/2014 AT 07:30 AM EST

After Joseph McStay and his family went missing in February 2010, Joseph’s father, Patrick, wanted to speak to his friends – even if it meant possibly speaking to his son’s killer.

He had a list of people he thought could have harmed his son and his family. One of the names was Charles "Chase" Merritt, 57, a business associate who worked with Joseph and helped with his decorative water sculpture company.

"I didn't have proof and I didn't know it was definitely him," Patrick McStay tells PEOPLE. "I had direct contact with him, so I had to try and keep that contact open to see what I could find out."

Patrick's suspicions were validated on Nov. 5 when Merritt was arrested on four counts of murder. He was charged for the deaths of Joseph McStay, 40, his wife Summer, 43, and their sons Gianni, 4, and Joseph Jr, 3.

The McStay family

McStay Family / ZUMA

Their bodies were found a year ago when a motorcyclist discovered a weathered skull while riding through the desert, nearly 100 miles away from the family's Fallbrook, California, home.

For many years following their 2010 disappearance, friends and family could only guess what would make the young family want to leave behind a successful business, as well as their beloved dogs.

Once their bodies were found, those same friends and family wondered who would want them dead.

"Joey was the best," says his father. "He was good. He was honest."

For more details about the case, read this week's issue of PEOPLE, on newsstands Friday