Four people have been arrested in connection with a shooting earlier this month that left eight high school students wounded at a transit bus stop in Northeast Philadelphia, authorities say.

The injured students, ages 15 to 17, were at the bus stop just before 3 p.m. on March 6 when three people exited a car around the corner, walked up to them and fired at least 30 times before fleeing the scene, according to Philadelphia Police Commissioner Kevin Bethel.

Police identified suspects using evidence that included two stolen vehicles, Deputy Commissioner Frank Vanore said during a March 11 news conference. Jamaal Tucker, 18, turned himself in, according to Vanore, and another 18-year-old, Ahnile Buggs, was arrested in the days prior. Each was being held with bail set at $16 million, Philadelphia District Attorney Lawrence Krasner said March 13.

A fourth suspect was arrested Tuesday in connection with the shooting, the US Marshals Service said. Asir Boone, 17, who was wanted for attempted murder, firearms violations and other charges related to the March 6 shooting, was taken into custody in Alexandria, Virginia, authorities said.

“I hope this final arrest brings some comfort to the student victims of this senseless crime,” Robert Clark, supervisory deputy US marshal for the eastern Pennsylvania violent crime fugitive task force, said Tuesday. “No child should have to fear for their safety while receiving an education and I hope these arrests can subside that fear.”

US marshals and Philadelphia police arrested a third suspect, Jermahd Carter, 19, on March 12 in Northeast Philadelphia, authorities announced that night. Carter’s bail was set at $4 million, according to the district attorney.

A spokesperson for the Defender Association of Philadelphia had no comment about its client Tucker when reached by CNN. An attorney listed on court documents for Buggs did not respond to CNN’s request for comment.

Police were working to find another two people seen in the vehicle, Vanore said March 11. “And we’re going to continually move with our investigation towards not only those individuals but this group, anyone who may have aided and assisted them – we’re coming for them, too.”

The case has raised concerns about safety on public transit and for the city’s students. Across the nation, firearms remain the No. 1 killer of children and teens, while 80 mass shootings have been recorded in the first 79 days of this year, according to the Gun Violence Archive, which tallies those in which four people, not including shooters, are hit by gunfire.

The eight victims shot March 6 include two 15-year-olds, five 16-year-olds and a 17-year-old, said Philadelphia police, with one 16-year-old shot nine times.

The attack came just days after a deadly Philadelphia shooting involving schoolchildren. In that March 4 shooting, one teen was killed, two other teens were injured, and two women on a bus were hit by bullets in an incident police labeled as “targeted.” Bethel, the police commissioner, said there “may be” a connection between the two shootings but “we still have a lot of work to do to make that formal connection.”

Philadelphia Mayor Cherelle Parker also addressed residents’ concerns about using public transit. “I hear you,” she said on March 11. “We want you to know that we are unapologetic about engaging every partner available to assist us in these efforts during these very tough times.” She added the city was focusing on “prevention, intervention and enforcement” to address public safety.

Authorities at the March 11 news conference encouraged witnesses or people with information about the March 6 shooting to share any knowledge with police.

Krasner, the district attorney, has said Tucker and Buggs are facing charges related to each of the eight victims. They include criminal attempt to murder, aggravated assault, firearms charges, possession of an instrument of crime, simple assault and reckless endangerment of another person.

“These defendants are potentially facing an enormous amount of time in custody,” Krasner said. “When you have eight different cases where you have engaged in atrocious violence, that is to be expected.”

Carter was wanted on suspicion of attempted murder, firearms violations and related charges, the US Marshals Service said in a news release on March 12.