Get em FBI!! Put this sick individual or individuals out of commission.
I really believe they have a serial killer.
Though I agree that the person is 'sick', they might not be an intentional serial killer.
Perhaps the motive is for a bar tender to drug the victims to where they are in a stupor, then other gang members rob them while "helping" them back to their rooms or "guiding" them outside to get some fresh air? If this is the motive, then the deaths may have been due to accidental over doses or dangerous experimentation with drugs while trying to get the desired effect.
My guess is that the motive could be purely cash based rather than politically based: Somebody trying to drug- then rob rich Americans. Instead, however, the targets are overdosed to the extent that they later die.Someone getting back at rich Americans?