PARIS — A high school student stabbed four other students at his school in western France on Thursday, killing at least one and injuring three others before being arrested, police said. The motive for the stabbing was unclear.

Such fatal attacks are quite rare in French schools.

France’s Prime Minister Francois Bayrou ordered tighter security outside and inside schools nationwide, and called for new proposals within four weeks for preventing and punishing knife violence by teens and children. He said metal detectors at schools could be considered.

The 15-year-old student stabbed four people with a knife during a lunch break at the private Catholic Notre-Dame-de-Toutes-Aides High School in Nantes near France’s Atlantic coast, a national police official said.

Teachers subdued him, and he was later taken in by police, the official said. The official was not authorized to be publicly named. The suspect had sent an email with unspecified grievances to all students just before the attack, students at the school told French media.

— The Associated Press