The Tarot Card Leaks

The card had a communications code on it so that the killer could communicate with the police. Police, code, call me God. Do not release to the press. So this was a direct message to the police. The sniper apparently wanted to contact them in the future using the code and let the police know who they were talking to. He thus didn't want this information released to the press because then anybody in the public would know the code and its value would be ruined as a communications tool.