The incident happened at around 2:30 p.m. on October 10 at Hope Avenue and Madison Street in Coatesville.
According to the Coatesville Area School District, a driver was transporting high school students when a bullet went through the windshield.
The school bus was reportedly hit twice: one in the bus grill and the other in the front window, sending glass into the driver's face.
None of the students on board the bus were hit by the gunfire.
Chester County District Attorney Chris de Barrena-Sarobe said four people were involved in the shooting, which investigators called a "targeted attack."
The Coatesville police chief said the suspects were targeting someone getting off of the school bus.
"Our investigation shows this is not some sort of school shooting, or someone trying to shoot up a school bus, or drive by. This was a targeted event where the actors were targeting someone getting off the bus," de Barrena-Sarobe previously stated.
No further information on the motive has been released.
Investigators said two of the four suspects fired two separate guns, and in total, eight shots were fired.
Jaki White-Marshall, 18, was taken into custody shortly after the shooting. Authorities said he was a student at Coatesville High School.
Bullet flies through windshield after Pa. school bus with students on board struck by gunfire
He was charged as an adult with with aggravated assault and other offenses.
On Sunday, authorities announced the arrests of Gabriel Johnson, 17, and Jose Medina, 20, both of Coatesville, Pennsylvania.
Johnson and Medina have been charged with attempted murder, aggravated assault, conspiracy, and other related offenses. Johnson was charged as an adult, authorities say.
"This is not the end of our investigation. We will continue to work towards arresting and convicting everyone involved in the shooting at this school bus," de Barrena-Sarobe said in a statement.
One other suspect is still being sought in this incident.
Anyone with information is asked to contact Chester County police immediately.