Rebecca Keller Killed Her 15-Year-Old Girlfriend's Mother — Where Is She Now?

A little after 1:00 a.m. on July 16, 2012, a young girl frantically called 911 from a neighbor's house where they lived in the Houston suburb of Humble, Texas.

Keri Murphy, age 15, said she heard someone break into their house through the back door. Then the screaming started. When police entered Keri's home, they found the body of 48-year-old Mary Ann Murphy. She had been stabbed more than 70 times.

While conducting a search of Mary Ann's home, police saw a broken window by the back door but noted it wasn't big enough for anyone to crawl through. It was also too far from the door, meaning no one could have reached in and grabbed the handle.

The house itself did not appear to be burglarized, which left investigators confused as to what the motive could possibly be. When they were eventually led to a young girl by the name of Rebecca Keller, things fell into place.

Keller is serving out a 60-year sentence at the William P. Hobby Unit, a women's prison in Marlin, Texas. She pleaded guilty to first-degree murder in October 2012. The gruesome story of Mary Ann's murder was featured in an episode of Investigation Discovery's Mean Girl Murders and goes into how Keller came to know Keri, which ultimately led to the two of them hatching a plan to kill her mother.

Keller and Keri met in the fall of 2010 at Chester W. Nimitz Senior High School, where Keller was a senior and Keri was a freshman. They were both in the choir, though Keller was in Varsity Choir. The two clicked immediately and started hanging out. Despite the fact that Keri was 15 and Keller was 19, a romantic relationship was formed.

"It was almost instant that they really liked each other. I think there was something magnetic there," said Olivia Smith who was responsible for intake.

This was Keri's first relationship with a girl, which didn't bother her friends at all. What did concern them was how Keri's parents might react as they were both devout southern Christians. Keri eventually worked up the courage to tell her mother, who was surprisingly accepting.

The trouble didn't start until Mary Ann discovered the age difference. She quickly forbids her daughter from seeing Keller. Not only did Keri not listen, but she began sneaking around in order to see Keller.

Things came to a head when Keri's father caught her and Rebecca in the shower together. By this point, friends described their relationship as toxic and unhealthy. Mary Ann threatened to call the police if Keller ever came to their house again but a couple of months later, she found them in bed together in Keri's room.

True to her word, Mary Ann had Keller arrested and took things a step further by getting a restraining order.

In July 2012, Keri and her mother were home alone when the murder happened. Based on what the police found, they suspected that Mary Ann was killed by someone already in the house. That's when Keri pointed the finger at a fellow classmate named Zein Ahmed, who was a loner thought to have had a crush on her.

She claimed to have asked Ahmed to come over and scare her mother but stumbled upon him stabbing her instead. For reasons that remain unclear, he confessed to the crime.

Nothing Ahmed said made sense, as far as the crime scene was concerned, and he soon recanted his confession. Police began looking closely at Keri, who had already been caught in two lies. They found a secret burner phone, which included texts between Keri and Keller. Both were arrested but Keri was bailed out by her grandmother.

That's when police heard a damning phone conversation while Keller was still in jail.

"I'm glad you didn't see what happened in there," Keller said to Keri. In response, Keri explained that she saw everything after poking her head into Mary Ann's bedroom.

"You weren't supposed to see. I told you to stay in your room," said Keller. After this, they both plead guilty. Not only is Keller in prison, but Keri received a 30-year sentence for her part in the murder. She is housed at the Christina Melton Crain Unit in Gatesville, Texas.