(CNN) - Seven people, at least five of them students, were shot Tuesday at a bus stop in Detroit, Michigan, officials said.

"Two perpetrators, possibly three, pulled up in a vehicle, exited their vehicle with weapons, asked for a person by name and then opened fire onto the crowd," said Police Chief Roderick Grimes.

"They got back in their vehicle and exited the scene."

Police Officer Leon Rahmaan described the vehicle as a green minivan and said the incident occurred about a mile from Cody High School at 2:30 p.m., as summer-school classes were ending for the day.

Two of the victims were in critical condition; the others were in serious condition at area hospitals, Grimes said. The shooters - both of them male - covered their faces with either masks or T-shirts, he said.

Robert Bobb of the Detroit Public Schools said summer school would continue Wednesday as scheduled.

"Tomorrow, we'll have new leadership in place at the school," he told reporters. "We want parents to bring their children, have their children continue to come to summer school here tomorrow."

No one was immediately taken into custody, said police spokesman Dan Donakowski.