The teen originally pleaded not guilty and not guilty by reason of insanity to alternate counts of first- and second-degree murder.
Meade County State’s Attorney Michele Bordewyk previously told the Journal that the boy and Ritthaler had been chatting online for a while but met in person for the first time when he killed her.
Ritthaler went missing Oct. 3 after being seen getting into a Jeep-like vehicle at a coffee shop in Moorcroft, Wyoming. She was found Oct. 7 in the basement of the home the boy shared with his mother east of Sturgis, near the Wyoming border.
Bordewyk, the prosecutor, said it’s unclear how an argument between the pair escalated to the boy ultimately shooting Ritthaler. She said the teen used a handgun that belonged to his mother, who was not home at the time.
Titus, the defense attorney, has said the shooting wasn’t planned and that alcohol and drugs were involved.
The teen will be held in the Meade County Jail until next week when he turns 18, Titus said, adding that he will then be transferred to prison.