State Police Lt. J. Paul Vance said Wednesday night the accident occurred after 6 p.m. near a public safety building on Mohegan Sun Boulevard.
He said a state police accident reconstruction team is investigating.
Mohegan Sun issued a statement saying it is "deeply saddened" and "our thought and prayers are with the family at this time. We are working together with officials and aiding in every way possible to assist with the investigation of this tragedy."
No further details were immediately released.