(CNN) -- Robert Zimmerman Jr., the brother of the man who shot and killed 17-year-old Trayvon Martin, apologized for his controversial and offensive tweets.
In one, Zimmerman juxtaposed a photograph of Martin with one of 17-year-old De'Marquise Elkins, one of two teenagers charged with killing a baby in Georgia.
Both Elkins and Martin appear to be flipping off the camera.
"A picture speaks a thousand words. Any questions?" the tweet reads.
In another tweet, Zimmerman writes: "Lib media shld ask if what these2 black teens did 2 a woman&baby is the reason ppl think blacks mightB risky."
Speaking on CNN's Piers Morgan Live on Wednesday night, he apologized for the messages, saying they weren't the "right thing to do."
"I realize those were controversial and offensive and I did publicly apologize for them," he said. "I'm a human being. I'm being upfront about what I did. I made a mistake ... Unfortunately (it) may not have helped George."
His brother, George Zimmerman, has been charged with second-degree murder. Zimmerman acknowledged shooting Martin but said it was in self-defense. Attorneys for Martin's family have accused Zimmerman of racially profiling Martin and shooting him "in cold blood."
Robert Zimmerman Jr. said he was trying to make a larger point in his tweets about the "media and their honesty in portraying the person who encountered my brother February 26, 2012.
"We've been led to believe that it's a junior-high-school-aged person because of the pictures," he said, referring to Martin.
"The analogy is these are two people who chose to represent themselves in this way. One was accused of killing a baby, and whatever's in his social media makes the rounds immediately ... However, the other person who almost killed my brother had he disarmed him -- my brother had every indication to believe he would have killed him -- his social media is off limits."
Zimmerman's tweets prompted a response from his brother's defense team.
Attorney Mark O'Mara told CNN's "Starting Point" Thursday morning that Robert Zimmerman doesn't represent his brother or his defense.
"Having said that, I'm not sure where (Robert's) heart was, but I've always said for the past year that we have to have a conversation about race, and the Zimmerman case has brought it to the forefront, particularly the way young black males are treated in the system," O'Mara said. "These type of tweets ... were insensitive to that, and quite honestly are the opposite of what I hope the conversation would be to try and figure out what's wrong with the system and maybe a good way to fix it."
O'Mara said he worries about how Robert Zimmerman's tweets will affect George's case.
"Everything that happens in this case is, if not overblown, hyper-focused upon, so that everything that George says or does is important," O'Mara said "... And certainly when a family member of my client says something that comes across as totally insensitive -- if not much, much worse -- (it) has an effect, and now we have to deal with it."