The Death of Josh Rubin

Josh Rubin was thirty years old when he disappeared from New York on Halloween night 2011.
The next day his remains were found on a country road in Pennsylvania. Josh had been shot in the chest and his body was burned. The only lead on this case is an HD picture of the suspects using Josh's credit card within 12 hours after his body was found. So, with such a great picture of the suspects, why hasn't anyone been arrested?