They did it in uniform. Amy Lange with Fox 2 News Detroit:
A Good Samaritan snapped photos of what appeared to be two men impersonating police officers involved in a pistol-whipping and robbery outside a Citgo gas station on Detroit's east side on July 21. Once Fox 2 aired those photos, an even more disturbing picture developed. … Now under arrest are two police sergeants, a 47-year-old officer and 20-year veteran.
Don't worry, everything will be ok, they have a Robocop statue.