An unidentified male handed money to Walker in exchange for the gun, Stanford said. Police are continuing to look for that person.
Walker, who has been charged with weapons offenses, conspiracy, and other crimes, allegedly concealed the handgun and entered the school at 5201 Old York Rd. police said. He was considered a guest in the school and did not have to pass through metal detectors, investigators learned.
An 18-year-old female student and a 17-year-old male student were hit by the same bullet. They were taken to Einstein Medical Center, where they were treated, police said.
According to police, Rochwell was said to be the target of an assault expected to occur after school. That may have been why he wanted the gun, police said. His bail was set at $500,000.
It was the second gun incident at a charter school in Philadelphia in less than a week. A 17-year-old student was taken into custody Wednesday after he was found with a loaded handgun in his backpack at the KIPP charter high school in West Philadelphia.
Charter schools have become increasingly popular in Philadelphia over the last decade, enrolling about 63,000 students this school year. Many parents have flocked to the schools, believing they offer a safer alternative.
Lawrence Jones, president of the Pennsylvania Coalition of Public Charter Schools, says that is still the case.
But, he said, "the reality is that charter schools enroll the same students as any other public school. Issues of social ills, issues of poverty, and issues of violence do not stop upon the enrollment application to a charter school."
All secondary schools in the Philadelphia district have metal detectors. Not all charter schools use them.
Jones said each charter school devises a safety plan for its students.
At Delaware Valley Charter High School, the administration posted a letter to the community on its website, promising heightened security when students return.
"We will have . . . mental health personnel available to all our students, teachers, and faculty members during this healing process," the letter said.
Chief executive and principal Ernest Holiday could not be reached for comment Monday.