One of three teenagers charged in the gang-related party bus killing in an Inver Grove Heights parking lot was captured Tuesday, more than three weeks after the shooting.

Still to be nailed down: Who fired the fatal shot that killed aspiring 19-year-old rapper 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.

“We are continuing to sort out who did what and when,” said Police Chief Paul Schnell. Schnell told the Star Tribune late Tuesday morning that the arrest in Minneapolis of 17-year-old Trashaun N. Morris, address unknown, brings all three suspects into custody.

Charged Monday in Dakota County District Court with first-degree riot resulting in death and second-degree assault was Samson Chu, 16, of St. Paul. Charged earlier with the same counts were Morris and 16-year-old Maurice Martin, of St. Paul.

The bus was letting off 40 to 50 passengers after a rolling birthday party celebration when the shooting occurred. Schnell said that a number of people who rode the bus “were quite intoxicated. Alcohol was certainly a factor.”

According to the charges, the bus was returning after a few hours of travel in the metro area. Passengers belonging to the “east side” group and others from a “west side” group argued throughout the trip. Schnell said the clash involved “rival gang affiliation.”

Fighting erupted about 1:30 a.m., as the east side group members stepped off the bus first and were chased though the parking lot by members of the west side group, the court filings continued.

Two east side members, Morris and Martin, turned and allegedly started shooting. Robles was hit in the chest. Chu was shot in the ankle and was pulled over later that night in a speeding vehicle in West St. Paul.

The charges against Chu said that he fell to the pavement upon being shot, pulled a gun and returned fire at least eight times.

The bus, painted pink, was rented by a woman for a birthday party for her younger sister, police said. Passengers ranged in age from 16 to the mid-20s.

Schnell said that once the murder investigation winds down, police will turn their attention to the bus company’s obligations to the well-being of its passengers.

The bus is owned by Safeway Transit in Farmington and is rented via rentmypartybus .com. Aleksey Silenko, director of rentmypartybus.com, said his company is cooperating with investigators.