A South Dakota teenager has admitted to slaying a 16-year-old girl who “ran away” from home to live with him after they met on an online dating website, authorities said.Michael Campbell, 17, pleaded guilty to first-degree manslaughter on Thursday for the death of Shayna Ritthaler, a 16-year-old from Moorcroft, Wyoming, who was reported missing from a local coffee shop on Oct. 3. Less than a week later, her body was found in the basement bedroom of Campbell’s home.“We got into an argument and then I shot her,” Campbell said during a change-of-plea hearing on Thursday, before referring to the teenager as his girlfriend, according to the Associated Press. “I shot her in the head.”Meade County State’s Attorney Michele Bordewyk said in court that the two teenagers met on an online chat and dating website, Badoo. After weeks of talking online, the pair eventually planned for Campbell to drive to Wyoming so Ritthaler could "run away and live with him in his house," prosecutors said in court on Thursday, the Argus Leader reported.On Oct. 3, Ritthaler was seen getting into Campbell’s car at a coffee shop about four hours outside of Cheyenne. Prosecutors say the 17-year-old then drove her back to his home in Sturgis, South Dakota, about an hour away.But back at Campbell’s home that he shared with his mother, the teenagers got into an argument. While Bordewyk said it wasn’t clear what sparked the argument, it escalated when Campbell grabbed a gun and shot Ritthaler once in the head. The 17-year-old shot her “without the design to cause her death,” Bordewyk said, according to AP. When asked by Judge Kevin Krull if he had any justification for killing Ritthaler, Campbell replied: “No.”On October 6, authorities found Campbell’s car and questioned him. The next day, Ritthaler’s body was found in his basement and the 17-year-old was arrested immediately.Many details surrounding the
shooting remain unclear because a Meade County judge sealed the case's affidavit on Oct. 10 at the request of the county prosecutor who cited the “potential publicity” of a case that had a “sensitive nature.”After his arrest in October, Campbell pleaded not guilty by reason of insanity with first and second-degree murder but changed his plea in Meade County Court as part of an agreement with prosecutors. The plea agreement dismissed the murder charges and recommended a 55-year
prison sentence. He will be sentenced on July 10. Steven Titus, the teenager’s defense lawyer, said Thursday that the killing was unplanned and said drugs and alcohol were involved. Krull also said that Campbell suffers from PTSD, but Titus said he would wait until sentencing to discuss his client’s mental state.Titus said he planned to make a “compelling case” as to why the plea deal and the 55-year sentence was fair, while Bordewyk said three of Ritthaler’s family members will make victim impact statements at the sentencing hearing. Campbell was being held on a $1 million bond at a juvenile jail in Rapid City. As part of his change of plea on Thursday, Krull told the teenager he was barred from making contact with the Ritthaler family for the rest of his life and he owed them more than $83,000 in restitution.