(CNN) -- A warrant has been issued for the arrest of a juvenile suspect in a shooting that wounded two students at a Philadelphia school Friday, police said Saturday.
The shooting occurred at Delaware Valley Charter High School.
The suspect is not in custody, but police expected him, accompanied by an attorney, to turn himself in Saturday.
Detective Don Suchinsky said Saturday that a second male held for questioning was released to his mother. Another juvenile was questioned and released Friday.
The shooter was in the school gym with seven other students, city police Commissioner Charles Ramsey said.
Some were playing basketball and others standing in a corner when he pulled a gun and fired.
The victims, a boy and a girl, both age 15, were hit in the arm. They were taken to a local hospital, police said, and their wounds are not life-threatening.
The Friday afternoon incident was at least the second shooting at or near a school this week in the Olney neighborhood.
The school went into lockdown as law enforcement officers searched students and let them out of the school, said police Lt. John Stanford.
The shooter had left the scene.
Not long after the lockdown, Philadelphia police posted a message on Twitter, saying they had a suspect in custody. They later released the 17-year-old male, who was "completely cleared by investigators," Stanford said.
What exactly happened remains unclear.
"We don't know the motives," Ramsey said, "don't know if it was an accident, don't know if it was intentional."
Surveillance video captured the incident, Stanford said. But police do not know how many shots were fired, his colleague Ramsey said. One bullet could have struck both victims. No shell was found at the scene.
Police searched for the weapon late Friday in trash cans, along railroad tracks and other spots around a nearby major urban transit station, transit spokesman Andrew Busch said.
Commissioner Ramsey seemed frustrated about school shootings reported across America.
"People send their kids to school; they shouldn't have to pick them up at the hospital," he said. "These kind of things just absolutely should not happen."