A French teaching assistant died on Tuesday after being stabbed several times during a bag search at a middle school in France.

The police arrested a 14-year-old student at the school in Nogent, a small town in northeastern France, according to the local authorities. Students, many of whom were in a state of distress after having witnessed the bloody scene, were placed under lockdown and then released to their parents throughout the day.

The attack reignited fears in France, where schoolteachers have been a target of increasing violence in recent years. The police have not yet disclosed a motive for the stabbing.

The French education minister, Élisabeth Borne, who rushed to the scene, told reporters that the student had been suspended twice early in the school year for disturbing class but had presented no difficulties since then. He had what seemed like a stable home and had been an anti-bullying ambassador at the school, she said. The student, who has not been named, had no criminal record, according to the local state prosecutor.

“His professors are totally shocked by what happened,” Ms. Borne told reporters on Tuesday afternoon.

Students who had been in line for the bag search, which was overseen by local police officers, were in a state of profound shock, she said, and a psychological support team had been put in place immediately.