BEIJING –  Seven students were killed Friday in a stabbing rampage at a middle school in China’s northwest, authorities said.

State broadcaster CCTV said the attack happened in Shaanxi province’s Mizhi county as students were leaving the No. 3 Middle School. It said 12 other students were injured.

A suspect identified by the surname Zhao has been arrested, it said.

China tightly restricts private gun ownership, making knives and homemade explosives the most common weapons employed in violent crimes.

No information was given as to a motive, although reports on Chinese social media said the suspect had once been a pupil at the school.