The grainy footage, released by police and broadcast on Chinese television, shows a crowd of panicked children fleeing the school before broom-wielding adults chase the attacker back into the street through the school gate.
No guards are visible nearby.
Television broadcasts did not show footage from inside the school buildings, but social media users were nonetheless shocked by the images.
“I couldn’t bear to watch it,” said one poster on Sina Weibo, a website similar to Twitter. “The number of hits suggests there is indeed lots of attention, but is it necessary to show it in this way? Are we way too tough?” Another asked: “How could this kind of terrifying video go online?”
The attack happened on the same day that 20 children were shot dead at a primary school in Connecticut in the US.