The McStay case baffled Southern California detectives: In February 2010, a husband and wife and their two young children vanished without a trace, leaving eggs on the counter and their dogs in the backyard. There was no sign of a struggle, and no hint of marital dispute or financial problems. Their bank account held $100,000.

For three years, there were no breaks in the case. Rumors swirled that the McStays had gone into Mexico and were involved in nefarious dealings with drug cartels. That speculation was sparked by surveillance footage of a family that resembled them moving across the border, as well as Google search queries on their computer.

Then, last November, shallow graves in the California desert were uncovered, and the remains of Summer, 43, Joseph, 40, and Gianni, 4, and Joseph Jr. 3, were identified.

Now San Bernardino County authorities have announced a triumphant conclusion to their lengthy investigation into the case. Sheriff John McMahon, flanked Friday by two rows of law enforcement officials and facing the families of Summer and Joseph McStay, described an inquiry spanning four years, 250 tips, 200 interviews, and 4,500 pages of investigation documents.

In a crime so mysterious, even minor details were revelatory: The family members, McMahon said, were killed at their house, and then their bodies were moved. Joseph McStay’s cause of death was blunt force trauma.

But the bombshell came when McMahon announced that Charles Ray Merritt, a 57-year-old father of three with a criminal record, had been arrested and charged with four counts of murder. For years, other theories had gone unproven, but Merritt, who had been Joseph’s business partner, continued to draw suspicion.

The story remains mysterious, and authorities are not revealing a motive yet. Last year, the reclusive, cowboy-ish Merritt gave a fascinating, in-depth interview to the Daily Mail to clear his name after the bodies were found.

In the late 1970s, Merritt had embarked on a string of criminal activity that would continue regularly for a decade. In the ensuing years, he was incarcerated on and off for a total of four years. After a decade-long pause, he served time again in 2001 for stealing $32,000 of equipment from an ironworks company.

Merritt joined Joseph McStay’s fountain design business, Earth Inspired Products, three years before the murders. The two were successful, and Merritt came to call McStay his best friend. According to Merritt, at the time of the killings they were thrilled about scoring a big deal in Saudi Arabia. The two spoke on the phone six to eight times a day. On the day of the murders, Merritt told police that they had spent 90 minutes together, making him the last person to see McStay alive. The last call made from McStay’s phone, at 8:28, was also to Merritt, which he says he did not pick up because he was watching a movie with his girlfriend. “I didn’t answer that call and I regret it to this day,” he told Daily Mail.

Merritt, coincidentally, was the first to alert police and the McStays’ family that the four were missing a few days later. He described going to their home, feeding their dogs, and growing worried.

Aware of his position as the prime suspect, Merritt volunteered to take a lie detector test shortly after the investigation got under way. He later said there were a few inconsistencies in the results, but he was let off. But he claimed to be hit hard by the murders, which he said cost him his entire business. Afterward he went bankrupt and said the stress caused him to split from his girlfriend.

Even Joseph McStay’s father didn’t believe that Charles Ray Merritt, who went by Chase, had anything to do with the killings. “What does Chase have to gain with Joey gone? Chase isn’t going to get the company,” Patrick McStay told CBS8 last year. “If you recall, Chase took a lie detector test and he passed.”

Merritt had refused media requests for years, but last year he told the Daily Mail he wanted to speak out to bring the case more publicity and bring the McStays’ killer to justice. He railed against the police for believing that the McStays had crossed into Mexico, implying that investigators were being lazy in their search.”[I]f anything I say can help jog someone’s memory or offer some clue, then I’ll be happy,” he said.

And until the end he proclaimed his innocence.

“I’m not the most perfect person in the world, I’ve made mistakes, I have even screwed people over a couple of times. I regret it, but that doesn’t give people the right to trash me, especially after I have lost my best friend,” he said.

“All I want is for them to find the a*******s who did this.”