OKLAHOMA CITY — A boy stood up and repeatedly stabbed a 14-year-old girl during an assembly at an Oklahoma high school on the first day of classes Thursday and she was airlifted to a hospital, a local sheriff’s spokesman said. Mark Opgrande, spokesman for the Oklahoma County sheriff, said the unidentified 14-year-old suspect is in custody. “They were having an all-school assembly … when for some reason a male student allegedly stood up and started stabbing a female student. Right now we don’t have a motive,” Opgrande said. Opgrande said the girl, who also was not identified, was in stable condition after being stabbed “multiple times … five, six, seven times” by the boy at Luther High School. Opgrande said he did not know what weapon was used. Opgrande said investigators were trying to determine what, if any, prior relationship the two students had. Opgrande referred other questions to Luther police, who did not immediately return phone calls for comment. School officials also did not immediately return phone calls for comment, but the school posted a brief statement on its Facebook page . “There was an incident at the High School Assembly this morning at the Auditorium. The situation is under control, all students are safe,” the statement said. The school has just over than 800 students, according to Oklahoma State Department of Education online records. Luther is a town of about 1,200 people about 25 miles (40 kilometers) northeast of Oklahoma City.