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Story highlights

NEW: Arrests made after 12-year-old Florida girl killed herself following hateful messages on Ask.fm and Kik

NEW: Two girls, ages 12 and 14, now charged with felony aggravated stalking in the case

"Why aren't you dead?" was just one of the messages Rebecca Sedwick received

Parents might know Facebook and Twitter, but kids have moved to other social sites

CNN  — 

“Why aren’t you dead?”

“You should die.”

“Wait a minute, why are you still alive?”

“Go kill yourself.”

It’s impossible to comprehend another human being, let alone a child, sending such hateful messages to another person, but according to Polk County Sheriff Grady Judd in Lakeland, Florida, these messages are all too real.

They were sent to 12-year-old Rebecca Sedwick, who ultimately jumped to her death in September, he said. The messages didn’t come via the social networking sites many of us are familiar with: Facebook, Twitter or Instagram. They were sent via newer, lesser-known social applications called Ask.fm and Kik, according to Judd.

“These apps are free, and as a result … you can either go up anonymously or create a fictitious identification, and you can torment other children, and it is frightening to see that occur,” the sheriff said.

Sheriff: Taunting post leads to arrests in Rebecca Sedwick bullying