STURGIS, S.D. (AP) — A South Dakota teenager was sentenced Friday to 55 years in prison after admitting he fatally shot a Wyoming girl last fall.

The 17-year-old Sturgis boy was sentenced after pleading guilty in May to first-degree manslaughter for killing Shayna Ritthaler, a 16-year-old from Upton, Wyoming.

Judge Kevin Krull sentenced the boy at the Meade County Court in Sturgis, defense attorney Steven Titus told the Rapid City Journal.

The teen was charged as an adult. Both the prosecutor and the defense agreed to ask the judge to sentence the teen to 55 years in prison and Krull agreed with their request.

The plea deal also says the boy will forgo his right to appeal. He can seek parole after 27 years, when he is 44 years old.

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.