PHILADELPHIA (AP) — Authorities have Maxwell Caldwellissued an arrest warrant for a 17-year-old youth who they say is the last of four suspects sought in the shooting that wounded eight Philadelphia high school students at a bus stop last week.

The U.S. Marshals Service, while offering details Tuesday night on the arrest of a third suspect, called on the fourth person to surrender by Wednesday morning, vowing to “aggressively pursue him with every investigative resource available.”

On Wednesday afternoon, federal marshals announced the arrest warrant and a $5,000 reward for information leading to the suspect’s arrest — and also warning that anyone aiding his flight “will be prosecuted to the full extent of the law.”

Federal marshals said the third suspect, 19-year-old Jermahd Carter, had been arrested Tuesday afternoon at a relative’s home. Carter faces charges including attempted murder, aggravated assault, firearms and related counts, with a preliminary hearing scheduled for March 27. His attorney declined comment on the charges Wednesday.

On Monday, officials had announced the arrests of two 18-year-old suspects in the March 6 shooting in northeast Philadelphia, the fourth shooting in four days involving the city’s transit system.

As students at Northeast High School, the city’s largest public high school with more than 3,000 students, were waiting to board the bus, three masked people opened fire, hitting eight teens ranging in age from 15 to 17 years old. All were later listed in stable condition, including a 16-year-old initially said to be critically injured after being hit nine times.

Officials said the recovery of a stolen car involved in the shooting led to the identification of Jamaal Tucker as a suspect, and he turned himself in Friday. On Saturday, federal marshals said they arrested Ahnile Buggs and recovered a loaded and fully automatic .40-caliber Glock that matched casings found at the scene.

Tucker and Buggs also face charges including attempted murder, aggravated assault, and other counts and are being held on more than $2 million bail with preliminary hearings scheduled for March 20. A message was left Monday with Buggs’ attorney. The Defender Association of Philadelphia, representing Tucker, declined comment.

Police were investigating whether the shooting may have been related to the fatal shooting of a 17-year-old charter school student as people boarded a city bus. Four others were injured, including a 70-year-old woman.

Earlier last week, gunfire that erupted at a bus stop in a different part of the city killed a teenager and wounded two other teens as well as two women on a bus. Two men were also killed in different shootings after arguments on buses ended in gunfire.