The reason Chris Brown's rehab stay was cut short is reportedly due to an incident which involved him throwing a rock through his mother's car window.
According to TMZ, Chris' mother came for a visit while he was serving his time at the facility, where she urged the singer to keep up his treatment. Chris was not happy with his mother's suggestion, and apparently threw a rock straight through her car window in a fit of rage. It seems that this was enough for the center to ask him to leave.
The acquired report went on to say that Brown's prognosis is "very guarded" without continuation of therapy, and a proper support network.
As previously reported, Chris will spend another 90 days in rehab, as decided in today's probation hearing.