After opening fire with a semi-automatic weapon at a Michigan high school, a 15-year-old boy murdered three classmates and injured eight others before being promptly apprehended, authorities said. According to the Oakland County Sheriff’s Office, one of the wounded was a teacher, while the others were students at Oxford High School in Oxford, Michigan, roughly 40 miles (65 kilometres) north of Detroit. The motive of the shooter was unknown, officials said. Those killed were a 16-year-old boy, a 17-year-old girl and a 14-year-old girl, Undersheriff Michael McCabe told reporters at the scene. Two of the wounded were in surgery and six were in stable condition, McCabe said. The suspect, a sophomore at the school, was believed to have acted alone and was arrested without resistance after firing 15 to 20 shots, McCabe said. “The whole thing lasted five minutes,” McCabe said. The suspect divulged nothing to police and demanded his right to a lawyer on being advised not to speak by his parents, McCabe said. “My heart goes out to the families enduring the unimaginable grief of losing a loved one,” President Joe Biden told reporters while touring Minnesota. The latest in a long line of school shootings in the United States is expected to rekindle arguments about gun regulation and mental health care, with many states allowing easy access to firearms while mental illnesses go untreated routinely. “This is a distinctively American problem that we must confront,” Michigan Governor Gretchen Whitmer stated after rushing to the scene and appearing with McCabe in front of the media. Student Abbey Hodder told the Detroit Free Press she was in chemistry class when she heard the sound of glass breaking. “My teacher kind of ran out and was scrambling,” Hodder, 15, told the newspaper. “The next thing I knew I saw he was pushing tables. It’s part of school protocol to barricade, so we all knew, barricade, barricade down. And we all started pushing tables.” McCabe praised the school for its preparation for a shooting and an orderly evacuation. The shooting underscored how students must decide when to emerge from a shelter once the gunfire stops. Video posted on social media showed students huddled in a barricaded classroom while someone outside shouts through the door that it is safe to come out, identifying himself as being with the sheriff’s office. However, the teacher says, “We’re not taking that risk,” and sceptical students who worried the gunman was luring them into the hall fled out a back window, where they were quickly met by uniformed deputies. “It is our plan to analyse it (the investigation) thoroughly and issue appropriate charges swiftly,” Oakland County Prosecutor Karen McDonald said in a statement. The suspect will be held in custody until the charges are filed.”