WINTER HAVEN,FLA (CNN) -- It all started with a boy.
The intense bullying that led 12-year-old Rebecca Sedwick to jump to her death last month stemmed from a dispute between her and a former classmate over a boy they had both dated, police said Tuesday.
And it didn't even end with Rebecca's September 9 death, said Grady Judd, sheriff of Polk County, Florida.
Authorities arrested two girls, including the 14-year-old girl alleged to have been Rebecca's chief tormenter, on Monday after the girl posted a taunting message on the Internet about what had happened.
"Yes IK I bullied REBECCA nd she killed her self but IDGAF," the Facebook post read, according to CNN affiliate WFTV. Judd said the initials meant "I don't give a (expletive)."
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Judd said the 14-year-old girl's family claimed her account had been compromised, but he said investigators don't believe that to be true.
After the girl's family refused to bring her in for questioning, Judd sent detectives to arrest her and a 12-year-old friend at their homes. The girls, whom CNN are not naming, are charged with aggravated stalking. They were booked Monday and the 12-year-old was released to her parents, Judd said. The 14-year-old remains detained.
"She forced this arrest today," Judd said of the 14-year-old's decision to post the message Saturday.
According to Judd, the girl was upset that Rebecca had once dated her current boyfriend and began bullying and harassing her more than a year ago when they were both students at a Florida middle school.
In addition to sending harassing messages over the Internet, the girl physically attacked Rebecca at least once, Judd said. She also recruited the girl's former best friend -- the 12-year-old charged Monday -- to bully her, Judd said.
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Among the online messages that drove Rebecca to jump to her death from the top of an abandoned concrete plant were, "You should die" and "why don't you go kill yourself," according to Judd.
The night before Rebecca killed herself, authorities say she messaged a boy she had befriended online, writing, "I'm jumping. I can't take it anymore."
Judd, clearly upset over the incident, expressed frustration that neither girl's parents were willing to bring them in for questioning. He said he was astonished to find out that the 14-year-old in the case was still being allowed to post to the Internet after what had happened.
He said he would charge the child's parents if he could, but said investigators were aware of no "obvious charges" against them.
"I'm aggravated that the parents aren't doing what they are supposed to be doing," he said.
While bullying Rebecca was not in itself against the law, Judd said, the girls' actions harassing her in school and online formed the basis for the stalking charge. He did not expect any other charges would be filed.
No court date has yet been set for the girls, who Judd said will likely not see any time in juvenile detention because they have no previous criminal records and the charge is a class 3 felony, one step up from a misdemeanor under Florida law.
Had Rebecca been 17 or older, he said, authorities could have filed nothing more than misdemeanor charges.
He implored parents to take more responsibility for the actions of their children online.
"We've lost sleep over that child dying needlessly and we want to see things change," he said. "We want to never, ever, ever investigate a case like that again."