DALLAS (CBS 11 NEWS) – Most people remember 16 year old Shania Gray as an outgoing athlete, who loved to sing and dance.

But to Franklin Davis, 30, she is the girl who accused him of rape.

And in a jailhouse interview, Davis detailed how he claims to have killed Gray and what led up to her death.

“It wasn’t me who actually came out. It was like a light switch, once it hit, a dark side came out of me,” Davis said.

Gray had babysat for Davis’ youngest daughter beginning in December of 2010. That’s when the two met, according to Davis.

“March 15th, I was accused of sexually assaulting her when I didn’t do it,” Davis said.

Charged with 4 counts of sexual assault of a child, Davis lost his job and subsequently could no longer provide for his 4 children. He says he began to have disturbing thoughts.

“I needed help because the thoughts, the depression that I was under wasn’t normal,” he said. “Nobody helped me.”

He says he sought help from a Pastor, who prayed for him, then called a suicide hotline but nothing worked.

With an October 29th trial date looming, Davis began an investigation of his own.

In an attempt to gather evidence on his own, Davis admitted to pretending to be someone else on Facebook in order to gain the trust of Shania Gray and talk to her about the case, even going as far as recording conversations.

Shania Ambriehl Gray went missing. The 16-year-old’s body was found near the Trinity River in Irving. (credit: Carrollton Police Department)

On Sept. 7th, Davis showed up to Hebron High School, to get in contact with Gray.

Davis told police she was scared when she saw him, but he assured her he wasn’t going to hurt her. He told her he wanted to talk about the sexual assault case.

She got in the car and they drove to Campion Trails, a park in Irving, where they both got out of the car.

Davis claims the two made a deal that Gray would deny everything.

Davis claims he had intended on leaving her there and told her wait five minutes until she called someone to pick her up.

“I turned around and walked off intending to leave her down there and it was like a different side of me came out,” said Davis.

He said he shot Gray in the back and she fell into the water, then he shot her again.

“It took her to say, ‘Why Wish?” to bring me back to who I was,” Davis said. Wish was a nickname Davis often used. “It switched back on and before I realized it, I stepped on her neck. She grabbed my foot for a couple of seconds.”

He held his foot there until she stopped breathing, according to Davis’ arrest affidavit. Then he apologized to her, asked for forgiveness from God, and rolled her into the water.

Davis is familiar with loss. His mother was murdered when he was 14.

“The exact same thing I went through at 14 losing my mama, I just reversed that whole process with somebody losing their daughter,” he said.

Now charged with capital murder, Davis says he is “100% remorseful” for what he has done.

He said he wants Shania’s mother to know that “I’m sorry.”

A vigil is planned Monday night 7 p.m. at Horn High School in Mesquite.