if you really care about the real world, well, there are totally 12,664 murders in 2011, and 734 of them are committed during a robbery, and among them 268 were committed by strangers (victims didn't have any relation with). However, there were 3,128 murders were committed during arguments (not related to felony), the single largest category of circumstances among all circumstances, and among1844 of them firearms were involved. You should worry more about having arguments with others, then somebody rob you.