Mattis vows to kill next person who calls him 'Mad Dog'

THE PENTAGON — Defense Secretary Jim Mattis has vowed to kill the next person who refers to him by the nickname of "Mad Dog," sources confirmed today.

After the secretary's press officer briefed him on the latest news outlet to refer to him by the nickname — which he claims a reporter just made up years ago — he asked for the name of the next "son of a b…