▶ Watch Video: Sneak peek: A Sister’s Fight for her Brother This past January, a young man was sentenced to two life terms for the murder of his parents, bringing a dramatic case to a close and leaving his sister devastated. When Brandon Pettit was arrested in August 2013 for the murders of his parents in Modesto, California, there was no physical evidence directly tying him to the crime. Instead, police based their case on things the then-25-year-old Pettit had said and done shortly before and after the murders. Lauren Pettit, Brandon’s only sibling, is convinced authorities got it wrong and believes her brother is innocent. The case against Brandon Pettit is reported by “48 Hours” correspondent Erin Moriarty in “A Sister’s Fight for her Brother” airing Saturday, May 15 at 10/9c on CBS. Scott and Janet Pettit, both 59, were found dead in their Modesto home in the early hours of August 8, 2013 by firefighters who were called to the scene on reports of flames shooting out of a bedroom window. Investigators quickly discovered the fire was no accident. Scott and Janet had been shot — a total of seven times — and accelerant was found scattered throughout their bedroom. Just over a week after the murders, police announced the arrest of the Pettits’ only son, Brandon, and someone police described as Brandon’s friend, Felix Valverde, who was 26 at the time. Law enforcement’s theory was that Brandon had paid Felix to commit the murders because, they say, Brandon was after his parents’ money and specifically, his dad’s prized 1961 Corvette. Scott Pettit driving his 1961 Corvette in a local parade. Mary Vecchione Both Brandon and Felix pleaded not guilty and Felix has yet to go on trial. Even though police had no physical evidence directly tying Brandon to the crime, what they did have were seemingly incriminating statements and actions Brandon allegedly made both before and after the murders. One example came from a woman named Sarah Wilson. Sarah and Brandon knew each other from high school and, according to Sarah, they had reconnected online in the months leading up to the murders. “I had some inclinations that he had a little crush on me. But I didn’t pursue anything with him. I didn’t give him any hints that I was attracted to him in that way,” Sarah told “48 Hours.” Sarah Wilson looking online at photos of the mansions in Georgia she says Brandon Pettit sent her. CBS News Sarah says it wasn’t long before Brandon made her a very generous offer — one she says she couldn’t refuse. “He had mentioned that his parents were going to buy him a million-dollar home in Georgia. And he said that I can move in with him,” Sarah said. Sarah says she went along with it but suspected it might be too good to be true. After all, she had never even met his parents. But Sarah says Brandon told her that was about to change. She says Brandon told her his parents had bought plane tickets for them all to go to Georgia to look at homes and that the trip was scheduled for August 9, 2013. A couple of days before that supposed trip, Sarah says she received a text from Brandon. “I got a text out of nowhere saying, ‘You’re getting a boob job for Christmas, LOL,'” Sarah told “48 Hours.” The text came in at 10:43 p.m. on August 7, 2013. Just a few hours later, Brandon’s parents were discovered dead. Brandon’s communications with Sarah would later be used as evidence against him, and Sarah would testify for the prosecution at trial. The prosecution would argue that Brandon sent Felix Valverde to kill his parents that night and that Brandon believed he would be able to fulfill the promises he made to Sarah with money he would inherit in the wake of his parents’ deaths. However, Brandon’s former defense attorney, Martha Carlton-Magana, says Brandon’s conversations with Sarah shouldn’t be given much weight. She points to Brandon’s Asperger’s diagnosis, which he received when he was in high school. Asperger’s is a developmental disorder affecting one’s ability to communicate. It now falls under autism spectrum disorder. Martha says that because of Brandon’s Asperger’s, he had a hard time developing relationships and making friends, so he would make up stories to try to get people to like him. “What about the fact, though … right before his parents died, he had texted Sarah Wilson and said for Christmas, you’re going to get … breast enhancement surgery? Just a coincidence, Martha?” “48 Hours” correspondent Erin Moriarty asked. “Yeah,” she replied. “Honestly?” “Yeah, I’m not sure it was the first time he said it, either…,” she said. Brandon’s sister, Lauren, also believes there’s nothing to Brandon’s conversations with Sarah. “I mean, that was just who my brother was … And … if I could, I, you know, could probably think back so many times where he, you know, would tell me, like, these crazy stories. And you’re like… ‘OK. No’,” Lauren told “48 Hours'” Erin Moriarty. “Words don’t make you a murderer.” But prosecutors say it was more than Brandon’s words. They say Brandon gave Felix Valverde the keys to the house and the ammunition to commit the murders. Learn more about the case in an all-new episode of “48 Hours.” Correspondent Erin Moriarty investigates in “A Sister’s Fight for her Brother” airing Saturday, May 15, at 10/9c on CBS.