More details emerging in the car crash that killed the wife of OKC Thunder assistant coach Monty Williams -- with cops telling TMZ Sports they believe the other car was speeding at the time of the accident.
Ingrid Williams died Wednesday morning ... hours after her car was struck head-on near downtown Oklahoma City by a car going the opposite direction that veered across the median. The other driver was also killed in the wreck.
Now, a rep for the OKC Police Dept. tells us speed appears to have been a factor -- "The other driver was clearly going at a fast rate of speed.