DULUTH — The former Proctor, Minn., high school football player charged with sexually assaulting a teammate last fall pleaded guilty Tuesday in Duluth juvenile court.

The 18-year-old, who was 17 at the time of the September incident, was set for a hearing to determine whether his case would be moved to adult court. Instead, an agreement was reached between the defense and St. Louis County prosecution for him to receive a juvenile court sanction, enforced until age 21, with an additional adult sentence enforced if he violates court orders.

Prosecutor Korey Horn said he had consulted with the victim and his family and "we believe the community is best served" with the agreement.

The Star Tribune typically does not name juveniles charged with crimes.

The teen, who attended the hearing with his parents, was charged by juvenile court petition in January with third-degree criminal sexual conduct — a felony — for assaulting a teammate with a plunger.

The investigation began in mid-September after a complaint of "student misconduct" within the football team. It led to the resignation of coach Derek Parendo and the cancellation of the football season. Proctor police completed their five-week investigation in late October.

According to police, over Labor Day weekend a third party sent a lewd photo to a group of Proctor football players on the social media platform Snapchat, using the victim's phone and Snapchat account. It prompted a response over the platform that the victim was "going to get the plunger." Interviews with football players revealed that a plunger was regularly used during "crass" locker-room behaviors, such as touching other players with the rubber end. None of those stories shared involved sexual assault, something the charged teen confirmed during Tuesday's hearing.

After practice Sept. 7, the petition says, the victim was in the locker room across the street from the high school when he was confronted by the suspect with the plunger. He fled outside toward the field, thinking it was another plunger joke, and was chased by the suspect and other players, at least some of whom allegedly held him down for the assault.

During questioning from attorneys and Judge Dale O. Harris Tuesday, the teen named six other players who allegedly chased, tackled and held down the victim, some he said also pulled down his pants. He confirmed he was the person who performed the attack, something he said he had "joked" to others he would do.

Witnesses told police they thought the suspect was joking until the moment he pulled the victim's pants down, and many reported being unsure who helped hold him down. After the alleged attack, the suspect threw the plunger at the victim, the petition says, and returned to the locker room saying, "I did it" and "I bet you guys didn't think I was going to do it."

On Tuesday, the teen said he didn't recall what he said at the time.

The school district of about 1,800 faced intense scrutiny in the wake of the incident. Student athletes became the subjects of taunts and jeering from opposing teams; many Proctor students were afraid to wear clothing that identified their school. Others, upset with silence from school leaders in the wake of another school-related sexual assault allegation, questioned whether the schools were safe.

Retiring superintendent John Engelking — who will be replaced by Kerry Juntunen — has said problems within the football program would be addressed. The Proctor School Board recently approved the hiring of a new football coach, Matt Krivinchuk, an assistant coach at Superior High School.

Disposition, which is akin to sentencing in juvenile court, is set for June 20.