Is it true that the Gracies had a hitman take care of Canadian NHB challengers?

I was at a party recently, and someone told me that the infamous NHB fighting family The Gracies hired a hitman to 'off' some Canadian martial artists who moved too fast for them to grapple with and subsequently defeated them in underground NHB fights??? Is this true?? I thought Gracie JuJitsu was undefeated in real fights?????????