TULLAHOMA, Tenn. - A killer's attempt to cover his tracks ends up helping put him away. Donnie Jones plead guilty today to killing a Midstate nursing student, and prosecutors say the conviction is thanks in part to evidence Jones accidentally helped preserve. Kelly Sharpton held her daughter's picture close as the man who killed her agreed to a plea deal that will keep him in prison for the rest of his life with no hope of parole.

"She was raped, she was brutally murdered," says Meagan Sharpton's mom Kelly. "My heart is open and bleeding and it will never close."

That heartache began last July when Meagan Sharpton, who was studying to be a nurse, answered a call from a man who wanted to meet with her about a job sitting with an elderly patient.

"She was excited," says Kelly. "She was gonna quit waiting tables and do more in line with what her career choice was."

Investigators say the whole thing was a ploy by Donnie Jones, who raped and shot Sharpton, then set her body on fire near Tim Ford's Lake.

"Our theory was the purpose of the fire is to destroy semen present in her body," says District Attorney Mike Taylor.

Taylor says the fire actually ended up preserving the evidence. That became key after investigators linked Jones to the crime through cell phone records and Sharpton's clothing found on his family's property.

"I attribute it to the Lord watching over us but at the same time a lot of hard work," says Franklin County Sheriff Tim Fuller.

Despite this plea, this case may not be completely over. Prosecutors are still looking at a person of interest, someone they say may have been an accomplice. Investigators declined to say much more, but the important thing for Meagan Sharpton's family is Donnie Jones headed to prison for the rest of his life. Sheriff Fuller says Donnie Jones tried to set up a similar meeting with another woman before he contacted Sharpton. Fuller believes that woman might have been a victim too if she hadn't decided to bring her mother, which prompted Jones to cancel the meeting.Man charged with slaying student pleads guilty