PITTSBURGH (AP) -- Three Pittsburgh high school students heading to their vehicle after classes ended were shot Wednesday, and another student was charged and told police he was retaliating for being beaten during a drug-related robbery last month at school, police said. Anjohnito Willett Jr., 16, was charged as an adult and in custody late Wednesday on four counts each of attempted homicide, aggravated assault and reckless endangerment. He's also charged with illegally possessing a gun as a juvenile. Willett wounded three students and shot at a fourth as they were headed to a car to drive home after Brashear High School let out at about 2:45 p.m., police Lt. Kevin Kraus said. The wounds of the victims, all boys, appeared to be non-life-threatening, according to police spokeswoman Diane Richard. One's head was grazed by a bullet, while another had a similar wound to his neck. The third boy was shot in the arm and foot and all three were in good or stable condition Wednesday night, Richard said. It wasn't immediately clear whether Willett had an attorney. He was in custody and awaiting arraignment, likely early Thursday morning, in Pittsburgh Municipal Court. Kraus wouldn't detail the October encounter that fueled the shooting but said Willett hadn't returned to school since. Pittsburgh Public Schools police investigated the Oct. 18 robbery but couldn't file charges because Willett wouldn't identify his attackers, telling investigators "he would take matters to his own account," Kraus said. Pittsburgh Public Schools spokeswoman Ebony Pugh confirmed that Willett hadn't returned to school and that officials were in touch with his parents. "I think they were considering moving him to a different location but it just hadn't happened yet," Pugh said. Kraus said police don't expect to charge any of the shooting victims in connection with the assault and robbery, which he characterized as drug-related without offering details. "If there's no victim, there's no crime," Kraus said. Witnesses initially told police as many as three gunmen emerged from the woods near the school, but Kraus said that turned out to be incorrect. One was another student cutting through on his way home. The other was a juvenile who was with Willett but not involved in the shooting. Police don't expect to charge him. "With the information and the evidence we have," Willett appeared to be the only shooter, Kraus said at a news conference late Wednesday. Brashear, with about 1,400 students in grades nine through 12 about two miles south of downtown, was locked down briefly, though students were released to their parents about 90 minutes after the shooting. Schools Superintendent Linda Lane said the school would be open Thursday, but would operate with a modified lockdown for the rest of the week. That means only students, teachers and those with previously arranged appointments will be allowed in the school.