There's finally justice in one of the most sensational murder mysteries in Southern California. The killer behind the execution-style slayings of Brad and Andra Sachs will finally pay for his evil crime. And it's none other than their own son, 22-year-old Ashton Colby Sachs.

It was February 9, 2014 when the wealthy couple, parents to five kids, were gunned down in the bedroom of their hillside Orange County mansion.

Immediately police determined at least one gunman entered the home at 2 a.m. and executed the couple.

It would soon be reported that the couple had gone through a bitter divorce, yet they were living together and sleeping in the same bed when they were killed.

The shooter would have to be someone who knew the property, the security system and the family's three dogs.

Then the investigation gets flipped upside down. In a twist no one saw coming, cops zero in on the most unlikely possible assassin: The Sachses' own son, Ashton.

He was supposed to be away at college in Washington, but cops would find a semi automatic weapon in his car and phone records reportedly placing him in the area around the time of the murders.

Prosecutors quickly worked out the chilling timeline, revealing Ashton meticulously planned the executions and carried them out with military precision.

Police say his sinister mission began when he drove 1,200 miles from college near Seattle to the family's sprawling 10,000-square-foot home in San Juan Capistrano.

Around 2 a.m. Ashton, dressed in dark clothes, entered the house and paced for about 15 minutes in front of his parents' bedroom before opening fire, pumping dozens of shots into their bodies.

"I just walked up and started shooting," Ashton says in a recording of an interrogation with investigators.

But Ashton's rampage wasn't done. He then moved on to shoot and paralyze his 8-year-old brother. He missed his 17-year-old sister. She would ultimately help authorities nab the killer in San Diego.

Ashton pleaded guilty to two counts of murder and attempted murder. But even with his confession came the burning question: Why?

The District Attorney's Office says Ashton portrays himself as a pathetic victim during the interrogation. The evidence paints a totally different picture, of a cold-blooded killer.

On Oct. 14, the judge threw the book at Ashton Sachs, with the most extreme punishment short of the death chamber: Four life terms plus an additional 100 years in prison.

At his sentencing the only family member to speak was Brad Sachs's sister, Ashton's aunt Lisa McGowan: "You had a choice, Ashton. You had apparently been thinking about what you were going to do for a long time. I've been told by my friends and family that I need to forgive you. Well, I can't forgive you today."