later, he returns and spits her in the face as she holds her child

This is the moment a thief attacks a mother in front of her two children, kicking her in the stomach, hitting her in the face and spitting on her, after she stepped in when he tried to rob a pensioner.

The shocking incident took place in central Stockholm, Sweden, earlier this month and was caught on security cameras.

The attack has caused outrage in Sweden, with the head of the police investigation swearing to catch the perpetrator 'if it's the last thing I do'.

Horrific: CCTV shows how the thief-to-be hits the mother across the face after she stepping in to stop him from stealing a wallet from an elderly woman at a Stockholm tube station

The video shows an elderly woman walking out of the Gamla Stan[Old Town] tube station and picking up her phone out of her bag.

As she answers the call, the perpetrator walks up behind her and tries to steal her wallet out of her open bag,

However, his attempt is foiled by a mother who is walking in the opposite direction with her two young children.

'The mother who sees this screams to the old lady to watch out, and pushes the man's hand out,' lead investigator Stefan Tellqvist with Stockholm City Police told SVT.

Robbery: The man notices that the elderly lady's bag is open after she has picked up her phone, and walks up behind her and puts his hand down her purse

Courage: The mother steps in and warns the elderly woman, and pushes the thief's hand out of her purse

Attack: The thief, who police is trying to identify, smacks her across the face and kicks her straight in the stomach as she is holding her child's hand

Vile: A few seconds later he returns, walks after the woman and spits her in the face as she is carrying her child in her arms

The thief then turns on the mother, who is holding the hand of one of her children, kicks her in the stomach and hits her across the face.

He walks off, leaving the woman in shock, and exits the station as she appears to be shouting something after him.

However, seconds later, he returns and runs after the woman and spits her in the face as she is holding her child in her arms.

'It is the worst thing I have ever seen during my years as a police officer, said Mr Tellqvist.

He adds that he is due to retire this year, and has now made it his mission to put the man behind bars.