A police chief in Bengbu, East China's Anhui Province said on Wednesday that his men were "slow but not timid" after video footage showed two police officers sat on their hands watching a 17-year-old girl being stabbed to death in front of them. 

An investigation team has been set up in response to the indignation of the victim's family who questioned why the on-site policemen did not stop the suspect during the incident.

The suspect, surnamed Shen, first bought a kitchen knife and a fruit knife from the supermarket in Majiazhen county, Bengbu, where the victim, surnamed Hu, had been working as a cashier for two months.

Shen stabbed the victim a dozen times in her chest and when two police officers, surnamed Cui and Song respectively, arrived, they watched Shen stab the girl over 10 times without stepping forward to stop the crime.

The entire incident was captured by the supermarket's surveillance camera.  

The video has been published by people.com.cn, which shows that the two policemen stood about two meters away from the victim and they threw a plastic stool and a paper box at the suspect after the victim stopped moving.

It was not until Shen stabbed himself twice and fell down to the ground did the policemen began to approach him. According to the video footage, the two police officers did not seize the opportunity to subdue him the first time Shen stabbed himself, giving the man the chance to stab the girl again.

One of the witnesses said the policemen were equipped with truncheons. "They could have stopped Shen, if they tried."

The head of the Public Security Bureau of Bengbu's Yuhui district responded through people.com.cn on Wednesday. "The two policemen shouted at the suspect but he still did not stop."

An anonymous law expert told the Global Times that the policemen should receive internal punishment for dereliction of duty, at the very least.

"The policemen could face a criminal charge," said the expert, adding that "if the policemen, as the witness said, did indeed have a weapon in their hands then the punishment will be harsher."