Brian Low was walking his dog on a remote country path when he was shot dead by a former colleague whose hatred had festered for years. The former groundsman's death was not treated as suspicious for several days, until a post-mortem examination confirmed he had died from gunshot wounds. He is now serving life for murder - but Brian Low's family still cannot understand the mistakes which were made after his body was found. They have spoken publicly for the first time in two-part BBC documentary Murder Trial: Death of a Dog Walker, which follows the police investigation and the trial. "I was so angry and so sad at the same time," says his brother Douglas Low.