The man approached a woman in a newsagency at a shopping centre in Ballajura in Perth's north on Sunday and grabbed her purse.
As he tried to run away, he crashed through a plate glass window next to a sliding door, shattering the glass.
He suffered cuts and was knocked to the ground.
He was initially helped to his feet by bystanders who were unaware of the robbery.
But an accomplice approached them and told the bystanders to leave the injured man alone.
The pair escaped in a stolen car.
Police are calling for anyone with information about the incident to come forward.