NATIONAL NEWS (CNN) — WINTER HAVEN, Florida (CNN) -- How much bullying does it take to drive a 12-year-old to suicide?
The father of the teenage girl in Florida accused of helping do that told CNN's "New Day" on Wednesday that his daughter wouldn't know.
And she has an alibi. It's him, he told Chris Cuomo.
Months of cyber abuse drove Rebecca Sedwick to climb up the ladder of a pair of silos at an abandoned concrete plant in September. She had already cut open her wrists in December but survived that suicide attempt.
This one she didn't.
Weeks after Rebecca leaped to her death, an incriminating message appeared in the Facebook feed of the girl accused of being her main tormenter, an estranged friend, age 14.
"Yes IK I bullied REBECCA nd she killed her self but IDGAF," the message posted Saturday on Facebook read. Grady Judd, sheriff of Polk County, Florida, said the online vernacular meant:
"I don't give a (expletive)."
The sheriff called the girl and her family in to see him about the post. Police arrested the daughter.
"She forced this arrest," Judd said.
Police have also arrested a 12-year-old suspect in the case. CNN is not identifying the two minors, who have been charged with aggravated stalking.
The 14-year-old couldn't have been the one to post that message, her father, Jose, told Cuomo. He is a witness to that. Jose and his wife, Vivian, do not want their last name revealed to the public.
Jose had just finished watching the news on TV when he found her asleep and sent her to bed. It was about that time that the note landed on Facebook, he said.
"I grabbed the computer and took it to my room, and the only other thing she could have used to send this message was this cell phone, and my cell phone is always with me," he said.
Jose suspects someone hacked her account.
The sheriff doubts that. Investigators don't believe her Facebook account was compromised, Judd said.
Over a boy?
Rebecca and her alleged bully were once friends, but they both had feelings for the same boy, police said. It soured their relationship.
The allegedly angry friend did not bully Rebecca alone. Police confiscated the laptops and cell phones of 15 girls at Crystal Lake Middle School, which Rebecca had attended.
They found a barrage of horrible messages:
"nobody cares about u"
"i hate u"
"you seriously deserve to die"
The bullied girl gave up on herself, Rudd said. "Rebecca wasn't attacking back. She appeared to be beat down."
Rebecca's suffering was no secret at her school. Teachers saw her in tears. There were fights, the sheriff said. In December, she was hospitalized after slitting her wrists.
Her school started a campaign against bullying, giving talks before the student body to discourage it.
The night before her deadly plunge, she send a message to a boy she met on Facebook: "I'm jumping. I can't take it anymore."
The girl's defense
The attorney for the 14-year-old girl stands by Jose's alibi.
Her client isn't responsible for the controversial post that led to her arrest, said Andrea DeMichael. The teenager has insisted to her: "This is not as clear cut as it seems."
The 14-year-old's parents said that they regularly check the online activity of their seven children, including their teenage girl's.
"I always check her Facebook. I know her password," Vivian told "New Day." She didn't see any vile messages. "If they're there, we didn't see it," she said.
But aside from that one incriminating message after Rebecca's death, the taunts reached her through other chat services, the sheriff said -- Kik and Ask.fm.
Her parents shook their heads and gave blank stares when asked about these sites.
Never heard of them.
"The only one that she had was Facebook, to our knowledge," Jose said.
DeMichael disputed there was any harassment or fight.
She said the 14-year-old and Rebecca did have a falling-out over the boy, and there was some "back and forth" at school between the former friends, but the girl never threatened Rebecca.
"She was actually upset at what happened to the victim," DeMichael said.
The 14-year-old's parents agreed. They had heard about another girl bullying Rebecca, but not their girl, they said.
Rebecca had trusted their daughter, who was her friend and brought her cares to her. Their daughter comforted her.
CNN's Steve Almasy wrote from Atlanta; John Couwels and Kim Segal reported from Winter Haven, Florida; and CNN's Marlena Baldacci and Sara Ganim also contributed to this report.