The shooting had the earmarks of a revenge attack, with the three wounded boys, all friends, suspected of having been involved in a fight with the suspected shooter last month, police said.
City police Lt. Kevin Kraus said at a Wednesday night news conference 16-year-old Anjohnito Willet Jr. faces four counts each of attempted homicide, aggravated assault and reckless endangerment, along with a gun violation. He said Willet, who was awaiting arraignment, would be charged as an adult, the Pittsburgh Post-Gazette reported.
The shooting outside Brashear High School in the city's Beechview neighborhood was reported about 2:50 p.m. EST, just minutes after students left the building for the day, the Post-Gazette said.
The newspaper said all three victims were boys, with one grazed in a leg and foot, another hit in the neck and shoulder, and the third grazed in the head.
City police Lt. Kevin Kraus said officers converged on an address about a mile away from the school and took six people, including a small child, into custody for questioning. The newspaper said Kraus did not explain their connection to the shooting.
Mayor Luke Ravenstahl called the police response "aggressive for good reason."
"We have a handle on what appears to be an isolated, a targeted incident," he said.
Pittsburgh Mayor-elect Bill Peduto said in a statement he was "pleased that "none of the injuries appear to be life threatening."
"While our officers were prepared for the worst," he said, "we are very pleased that the shooting did not occur in the school or on school premises."
Pittsburgh Public Safety Director Michael Huss said the shooting scene, which was not on school property, had been secured.
While initial reports indicated there may have been up to three gunmen involved, Kraus later said investigators now believe only Willet and another juvenile were involved. The second youth was not facing charges now, he said, adding a third youth seen at the time was just cutting through the area.
Kraus said police believe the shooting was tied to an Oct. 18 fight near the school that may have been drug-related in which Willet was physically attacked by the three shooting victims. Willet did not press charges in that case.
Brashear High has 1,416 students, the most of any public high school in the city.
Pittsburgh Public Schools Superintendent Linda Lane issued a written statement saying both Brashear High and South Hills Middle School would be open Thursday but would be on a modified lockdown the rest of the week with only students, staff and visitors with scheduled appointments allowed inside.
"We are taking this matter seriously and focusing on the safety of our students," Lane said. "Our thoughts go out to the families of the victims."
Danielle Eberhardt told the newspaper her son, Robert Eugene Minor III, was shot in the neck. His father, Robert Minor, said his son was stable.