I'm an attorney in Florida. I am a former prosecutor and handled prosecuting these cases for the state. Now, as a defense attorney, I've handled several Baker Acts from the defense side as well.
As I suspect you know, Florida's Baker Act permits people to be involuntarily civilly committed if they are thought to be a danger to themselves or others based on mental health issues. According to law, the person can be held for up to 72 hours without a hearing.
During that time, the person is to be examined by at least one doctor. If, after an examination, the person is not considered to be a danger, they can be released. If, after an examination, the person is considered to be a danger, then the hearing must be held.
At the hearing, a judge makes a determination as to whether the person appears to be a danger. If so, they can be committed for a longer period of time.
If your brother was released, either before or after the hearing, then he is not subject to being re-committed. Having said that, if another report is made about his well-being he could be committed a second time under the Baker Act.
Also, several customers have asked how they may direct a question to me in particular. If you specifically want me to assist you in your legal matter, just put "FOR JOSEPH" in the subject line and I will gladly pick up the question as soon as I am on-line.