I just can't see how this young man was put up to murdering Cali by the mob. Sometimes the simplest explanation is the best explanation. There are too many variables that can go wrong if the mob use an irrational cat like this as a patsy.
anyway if he didn't even know his niece, how he found the adress and why cali? he typed on google 'gambino family' and chosed cali as a target because among the leaders?
maybe really somebody adviced it to do the murder
