Story highlights Prosecutor says he has 30 days to decide how to charge the girls

Judge sets bond for parents at $20,000 and assigns public defenders

Parents were out of town and left child unattended, police say

(CNN) It could be weeks before the public knows if 11- and 15-year-old sisters will be charged as adults in the shooting death of their brother, as a Florida prosecutor has 30 days to make his next move in the fratricide case.

At a Wednesday news conference, State Attorney Jeff Siegmeister said the teens will be detained 21 days, plus an additional nine days -- one at a facility in Ocala, the other at a Gainesville detention facility -- while he makes his decision on what charges they will ultimately face and whether they will be treated as juveniles or adults.

So, what would compel the sisters to allegedly kill their older brother? Some mean treatment, they told police.

However, Columbia County Sheriff Mark Hunter told reporters that it wasn't clear what led to the shooting.

"The motive has yet to be determined," he said. "There's going to be 100,000 whys. We might not ever know why this child acted out like this."

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