This is episode one of Off Duty, a new Guardian Investigates podcast series by Melissa Segura. On the evening of 29 December 2011, the police officer Clifton Lewis was moonlighting as a security guard at a Chicago minimart when two men walked in. They shot Lewis several times, then took off with his gun and police star. A week later, police had their suspects: four men affiliated with a gang called the Spanish Cobras. For hours, under intense police questioning, they all denied doing it. But that did not seem to matter. You can find the rest of the series on Apple, Spotify, or wherever you listen to your podcasts