Helio Gracie is the man who founded the Gracie Jiu Jitsu (Brazilian Jiu Jitsu) school of fighting. It was his family that gave us the Ultimate Fighting Championship, which proved that grappling and groundfighting can be effective against striking martial arts. From this, submission grappling is now one of the fastest-growing martial arts/combat sports today.
His passing away marks the ending of an era. No longer will we have that experience and authority with us. However, he has left us a great legacy and a large family, from which we will continue to learn and grow.
Helio Gracie on Wikipedia
Helio Gracie on the Gracie Academy website