>>> we're back with a wake-up call for parents whose kids are getting to that stage when the computer and the cell phone become a big part of their lives. experts say parents should be aware of possible online bullying, a problem highlighted once again this past week with the death of a young girl in florida. her mother says she was continuously bullied, not only at school, but through social media apps on her phone. we get the story tonight from nbc's charles hadlock.

>> 12-year-old rebecca of lakeland, florida, lived in a tortured world online . no one knew until rebecca 's mom saw the texts on her daughter's cell phone .

>> they were saying mean things to her, telling her why don't you go kill yourself, you're ugly, you're stupid, nobody likes you.

>> reporter: police believe the vicious texting conversations may have led her to change to a platform at this abandoned cement plant last week and jump to her death.

>> i just can't believe she is gone. she was only 12.

>> reporter: making her one of the youngest children to apparently commit suicide after being bullied online.

>> some of the juveniles have told us that rebecca was absolutely terrorized on social media by some girls.

>> reporter: the abuse started more than a year ago. rebecca 's mother pulled her out of school, closed her facebook page, and changed her cell phone number.

>> the bullying continued by a group of female juveniles on different social media outlets such as kick, skqfm, instagram.

>> there are a lot out there that ask you in a private way where you are user name to user name , and parents would have no idea that's going on.

>> reporter: although most social media apps are not meant for kids under 13, experts say they've become a tool for kids to bully other kids.

>> very easy for some cyberbullying to snowball, and everyone starts joining in and group text messaging people.

>> whether it's the parents of the bullier or the parents of the bullied, either way , parents need to pay attention what their kids are doing.

>> reporter: an online tragedy with real world pain. charles hadlock, nbc news.