If it was billionaire mayor Michael Bloomberg as the well-founded rumors suggest, he would have had to do it anonymously, and wash the money pretty good, because it’s illegal to buy guns like that across state lines. Buying 2,000 guns that way would be 2,000 federal and state felonies.
Giving money to someone else to buy guns for you — knowing you can’t buy them yourself – would be a “straw purchase,” something mayor Bloomberg knows is strictly illegal, since he has been fighting against straw buyers publicly for a long time. We don’t know who put up the cash and he sure isn’t saying. The crime doesn’t require that the true buyer ultimately receive the guns, just that the money moves through a knowing straw man (or woman).