More than two months after gang-related gunfire killed a 19-year-old man outside a party bus in an Inver Grove Heights parking lot, prosecutors say they determined that a 17-year-old St. Paul boy fired the fatal shots.

Trashaun N. Morris was charged Tuesday as a juvenile in Dakota County District Court with second- and third-degree murder, crimes committed for the benefit of a gang and second-degree assault. A motion to try Morris as an adult remains pending.

Information from witnesses, and analysis of shell casings and bullet fragments led investigators to conclude that Morris killed Billy Ray Robles of St. Paul on March 24 outside the AMC Inver Grove 16 theaters just off Hwy. 52 and south of Interstate 494.

Also charged as juveniles with first-degree riot were two 16-year-olds from St. Paul, Maurice Martin and Samson Chu, 16. They pleaded guilty and are serving suspended four-year sentences. If either violates the terms of their sentence, the prison term could be imposed in adult court.

The only adult accused of a crime, 18-year-old Taishawn T. Smith of Crystal, is charged with second-degree riot. A witness said Smith was fighting with “everybody that was not his friends,” the complaint read. Smith told police that he was acting as a “peacemaker.”

The bus was letting off 40 to 50 passengers after a rolling birthday party when the shooting occurred. Police Chief Paul Schnell said numerous passengers were intoxicated.

According to the charges, passengers belonging to the “east side” group and others from a “west side” group argued throughout the trip. Fighting erupted about 1:30 a.m. as the east side group members stepped off the bus and were chased through the parking lot by members of the west side group.

Two east side members, allegedly Morris and Martin, turned and started shooting. Robles was hit in the chest. Chu was shot in the ankle. The charges against Chu said that he fell upon being shot, pulled a gun and returned fire.

The bus, owned by Safeway Transit in Farmington and operated via rentmypartybus.com, was rented by a woman for a birthday party for her younger sister, police said. Passengers ranged in age from 16 to their mid-20s.