For the past nine months, John Borgen, 13, of Lakeland, Fla., has been dating the 14-year-old girl police charged with felony aggravated stalking in connection with Rebecca's death. But he says he dated Rebecca, 12, before becoming involved with the 14-year-old.
"I think about her [Rebecca] almost every day," wondering whether "I could have stopped it," he told ABC News in an interview Thursday night.
Police arrested and charged the 14-year-old girl earlier this week with taunting Rebecca online and at school.
Police say the 14-year-old suspect is one of the girls who told Rebecca in online postings she should "drink bleach and die" and should "kill herself" because she was "ugly." But police say perhaps the worst of the alleged bullying case came after Rebecca of Lakeland, Fla., jumped from a concrete silo tower to her death Sept. 9.
Polk County Sheriff Grady Judd accused the teen of gloating on Facebook after the suicide about bullying Rebecca.
John said, "I thought somebody else did it. I thought somebody hacked her account, but when she was being charged and arrested, I was like why didn't she tell the police that somebody got into her account or got her password or something?"
The sheriff released the names and mug shots of the accused juveniles earlier this week to send a message to others in the community about cyberbullying. ABC News is not revealing either girl's identity because they have been charged as juveniles.
The parents of the 14-year-old suspect told ABC News earlier this week that they monitored their daughter's Facebook activities nightly and saw no signs of bullying, leading them to believe someone hacked her account.
When asked whether he was ashamed of his girlfriend's actions, John said, "It's like mixed feelings. One day tells me I'm tired of all of this bullying. This part tells me every day I'm tired of the bullying, because I don't want to see it again.
"But at the second part, it's like, I still don't believe that she did it. But the fact is that she still bullied her, she should never have done it."
John said he never saw his girlfriend or the 12-year-old suspect, who has also been charged with felony aggravated stalking, bully Rebecca online or in person.
Meanwhile, at a town hall meeting at Crystal Lake Middle School in Lakeland, Fla., Thursday night, Sheriff Judd revealed new information that there were clear warning signs Rebecca wanted to end her life. Judd said he saw postings on her Facebook wall asking, "how many over-the-counter drugs do you take to die?"
"We must talk to our children, we must give them the opportunity to open up," Judd told parents.
John says bullying is a problem at Crystal Lake Middle School, where he Rebecca and the two suspects all went to school.
"I have seen bullying at school, and I almost got into a fight because they were bullying," he said. "They were jumping my friend ..., and I pushed the other kid out of the way and told him, 'You don't need to be stepping on him,' and we almost got in a fight, but everybody was holding me back," John said.
John says he is now on a mission to expose bullies and urges anyone who is a victim of bullying to speak up and alert others. He says Rebecca and the alleged bullying are something he thinks about every day.
"I think about her almost every day. That comes to my mind almost every day," he said, adding, "I could have stopped it."