Police found 19 spent shell casings scattered in the San Diego street where Gregory Benton was murdered on April 12, 2014. Benton and his cousin had gone to buy cigarettes, a witness later said. As they returned to a family party, two men pulled up in a car behind them. They got out, and at least one of them opened fire. Witnesses didn’t get a good look at the men or the car, so when police sat down to review their leads, the shell casings were the best evidence they had.