Messages appeared to indicate the girls planned to kill themselves after the murders took place, including one with included the phrase "thank Satan", according to police.
Two middle school girls in Florida planned to go on a stabbing spree and kill several students Tuesday, according to WTVT.
The girl's mother called the school and the assistant principal found the students in the bathroom, Hall said.
Bartow Police Department said the pair planned to wait in a school toilet until smaller pupils entered.
A staff member, however, caught them hiding in a school bathroom with several weapons, according to police. The child's mom told school staff that they must be mistaken, setting off a campus search.
A hand-drawn map of the school was found during a search of the girls' homes.
Hall said the girls emptied their pockets onto Principal Christopher Roberts desk and one of the girls produced a paring knife and a sharpener. Messages on their cellphones also stated they wanted to leave body parts at the school's entrance, WKMB reported.
Both girls face charges including conspiracy to commit first degree murder.
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Police said the girls planned to kill as many as 15 students.
Additional police were already on campus because a student had notified a teacher of a rumored threat to students.
The girls were reportedly found with several items the police believe they meant to use to harm others, including a pizza cutter, butcher knife, paring knife, and sharpener.
Chief Hall said the girls made comments "that they were willing to drink blood and maybe possibly eat flesh".
"I don't think either one of them was a ringleader", he added.
Prosecutors will determine whether the girls will be charged as juveniles or adults, Deputy Police Chief Bryan Dorman told the Associated Press in an email.
"I'm going to call them small children, only 11 and 12 - seriously sat down and plotted to do serious bodily harm to another student at school", Hall said.
Polk County Schools Superintendent Jacqueline Byrd said at Wednesday's news conference that the district will be filing for expulsion of the students, and that she was not aware of the two students having any prior disciplinary problems. Knives, scissors and a pizza cutter were also found, according to Fox 13.