Assad was found unconscious in a restroom at Pechanga Resort Casino in Temecula, California on the morning of Aug. 31, the sheriff's office said.
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"Assad died from her injuries sustained in the incident," the office said Wednesday.
The Press-Enterprise reported that the she appeared to have been subject "to a great amount of force, such as being pushed, thrown or punched."
Williams and Candace Townsel, 39, both of Moreno Valley, were arrested on suspicion of murder and robbery, sheriff's officials said in a statement.
Casino security helped investigators with the case, according to the sheriff's statement.
Williams was being held without bail and Townsel was being held in lieu of $1 million, NBC Los Angeles reported Saturday.
The NBC News affiliate said Williams' no-bail status was the result of her connection to Leonard, who has a $103 million contract with the Clippers.Leonard, a forward, joined the Clippers in July from the Toronto Raptors as part of a two-year deal with an optional third year.
Leonard was a basketball prodigy at King High School in Riverside when his father was killed by a gunman at his car wash in Compton in 2008.