San Bernardino County sheriff's deputies were called to the casino around 5:11 a.m. Wednesday on a report of two unresponsive people found inside a vehicle.
They found an adult male and adult female who were unresponsive and appeared to have suffered gunshot wounds. Both were pronounced dead at the scene.
Investigators say they "are not looking for any outstanding suspects."
The identities of the victims have not yet been released.
Anyone with information is asked to call Detective Michael Warrick or Sergeant Greg Myler at (909)387-3589. Anonymous tips can be provided to the We-Tip Hotline at 1-800-78CRIME (27463) or online at www.wetip.com.