Robert Zimmerman had been making the rounds in traditional media, granting interviews in an attempt to clear his brother's name and blunt charges he was acting with racial bias when he shot and killed Martin, an unarmed black teenager.
Just after midnight Tuesday, Zimmerman fired off a series of tweets directed at Natalie Jackson, the lawyer representing Martin's family, vowing he would expose her actions and see her disbarred, the Miami Herald reported.
"I hope GOD grants you a long life so you live to repent for what you have done," one tweet read.
"My Life's work = you WILL be held accountable for your words/actions. You AINT seen NOTHIN' yet ... I will see U disbarred," said another.
George Zimmerman lawyer Mark O'Mara said he sympathizes with the "noble goal" of trying to clear the family name, but encouraged Robert to be careful not to harm his brother's legal defense.
"I have been cautious with how we act in this case and now someone with the same last name who does not act with the same constraints is out there -- and I have no control over him," O'Mara said. "But they do have to be sensitive to the environment in which we are telling this story. No matter what, George is still at risk here. And we still have a dead young man -- that's fresh on everyone's mind. That frustrates me."
George Zimmerman shot Martin Feb. 26 in the Florida housing complex where Zimmerman was a neighborhood watch captain. Martin was walking home from the store when Zimmerman confronted him. Conflicting accounts of what happened next have been given, but Zimmerman ended up shooting Martin, who was unarmed.