Brutal moment knifeman stabs woman in face and chest after she holds lift door open for him

A shocking video shows the moment a man stabs a woman in the face and chest after she held a lift door open for him.

The distressing CCTV footage captures the man entering the elevator, which is being held for him by a woman at a railway station in Huntingdon, Philadelphia.

After the man steps into the lift, the pair appear to have a short conversation before he suddenly takes out a knife and attacks her.

In the clip, the woman is seen falling to the ground and dropping her purse, but the man does not pick it up as someone would in a robbery.

Officers confirmed the woman, 30, suffered several stab wounds and was taken to hospital, where she is now thought to be in a stable condition.