Police are investigating a smash and grab robbery at a Brantford jewellery store on Friday.A man entered the store on King George Rd. around 3 p.m., smashed several display cases and stole a number of rings.Police say the man ran out of the store and dropped the rings. They believe he cut himself during the robbery.The suspect is described as 20 to 30 years old, slim, wearing a black bomber style jacket, grey pants and black and white shoes. He was carrying a yellow “J.R. Cigar” plastic bag. Anyone with information is asked to contact police.