I'm sure most members already know this, but as a former ref I feel it needs to be stated again. There are rules specific to taunting, which I believe this is what the Virginia players did to Gavin. Here is an excerpt from Rule 5 - Personal and Expulsion Fouls:
"Unsportsmanlike Conduct SECTION 4. No player, substitute, nonplaying member of a squad, coach or anyone officially connected with a competing team shall:
a. Enter into an argument with an official (maligning) as to any decision that has been made or in any way attempt to influence the decision of an official.
b. Use threatening, profane or obscene language or gestures at any time before, during or after the game.
c. Bait, taunt, call undue attention to oneself, or commit any other act considered unsportsmanlike by the officials. Baiting and taunting is a one- to three-minute nonreleasable foul in all cases.
Note 1: If a player continues to be abusive after the penalty is assessed, the official may add additional nonreleasable fouls. Penalty time from these fouls counts toward the five-minute limit for fouling out. If a coach or bench players continue to be abusive after the penalty is assessed, the official may assess additional nonreleasable penalties that shall be served by an additional attack player (see Rule 7-4). Flagrant misconduct is an expulsion foul. (see Rules 5-13 and 5-14.) An expelled individual is barred from being in the competition area, including the spectator area."
Do the officials need to warn a player involved in taunting? Not really, they can just throw the flag. Is that what I would have done? Probably.