OSCEOLA COUNTY, Fla. (CBS12) — A Florida man was sentenced to life in prison for the murder of his girlfriend's 13-year-old daughter.

On Monday, Stephan Sterns pleaded no contest to the murder of Madeline Soto and was found guilty of sexual battery during a hearing in Osceola County.

The Orange County Sheriff's Office (OCSO) said during the investigation that Sterns was Madeline's mother's boyfriend -- and the last confirmed person to see Soto before she went missing, a day after her birthday party on February 26, 2024.

As deputies looked into her disappearance, they reported finding "disturbing images" of Madeline that were "sexual in nature" in Sterns' phone, leading to his arrest. They also said a review of the phone's data revealed attempts to delete evidence.

On Feb. 28, 2024, Kissimmee Police, working with the Orange County Sheriff's Office, arrested Sterns for sexual battery and possession of child sexual abuse material after finding disturbing images and videos on his phone.

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The plea deal comes just a day before Sterns was set to go on trial for the charges of sexual abuse. Although he faced the possibility of a death sentence, the judge sentenced him to life in prison without parole as part of the plea agreement.

The Osceola County courtroom was a somber scene with Madeline's father, Tyler Wallace, stating, "Because of the actions of this depraved man, I will never meet the woman she was becoming. You're weak, you're a coward, you're a sneak thief, you crept into a family and took advantage and exploited them when they were weak."

"I have so much hatred in my heart, specifically for the creature that's sitting in this room today. And no matter what happens or what just could be brought, it kills me that it doesn't bring you back," said Madeline's aunt, Letizia Nunez.

Sterns made a remark during his sentencing, stating, "I agree that it's not fair that Madeline is not here anymore. I still have a hard time contemplating a world where she's not around a world which feels less vibrant and less colorful than it did before. I have nothing but sorrow for her loss, and I miss her all the time."

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