I can't find any public report stating the reason for Mr. Brown's "firing," if you can call it that when he's still getting paid, though he was asked to gather his belongings and sent home before a new, interim chief was appointed.
Miller also pointed out a report I hadn't seen regarding three other UT-System police chiefs fired last year. From Campus Safety magazine ("Three police chief dismissals trigger UT department review," 9/1/09):
After the dismissal of three campus police chiefs in one year, the University of Texas (UT) System will create a special panel to review operations at all UT campus police departments, according to mysanantonio.com.
In July, David Hernandez resigned from his position at UT-San Antonio following allegations of sexual harassment. UT-Dallas’ police chief, Colleen Ridge, stepped down from her position after officials investigated complaints that Ridge was using her state-leased Honda Pilot to run personal errands. Last September, Howard Miller was fired as police chief at UT-Pan American. The details of his termination have not been made public.
Additionally, officials for the UT System have noticed “operational irregularities” in its departments.
Lately Grits has called into question the quality of supervision at peripheral departments like campus police, and UT firing four of its 14 campus police chiefs within a year's time contributes to that impression. I know our friend "College Cop" will arrive in the comment section soon to let us know we shouldn't draw conclusions from an isolated incident, or from four isolated incidents, or whatever, but it's a recurring theme that the supervisory talent pool among law enforcement just isn't deep enough for 2,500+ agencies across Texas. Too often, as in this instance, campus police departments operate in clubby environments with less professionalism or internal accountability than one generally sees at municipal PDs and Sheriffs.