Tilman Fertitta -- the man who just bought the Houston Rockets -- is working with the Vegas casino he owns to help victims and first responders affected by the mass shooting, TMZ Sports has learned. 

Fertitta owns the Golden Nugget -- and we're told he's personally been on the phone with hotel management to help strategize how they can best use their resources to help out. 

We're told the Nugget has already reached out to MGM Resorts to help house families of people killed or injured in the shootings. With more than 500 people injured, lodging could be an issue and Fertitta wants to make sure the families are taken care of. 

The Nugget says staff is also offering meals to first responders and participating in blood drives -- while working on a coordinated long-term plan.