The numbers are probably accurate. This sounds like it was some sort of gang initiation.
Milwaukee's inner city is a cesspoool. People generally don't care as long as the thugs only prey on their neighbors.
If you watch this develop you have two things working.
First is the 11 year old campaigning for a lesbian relationship with the 16 yr old girl who was arrested, and second, I suspect that it will come out that this was gang related and that the actions were gang initiation.
That doesnt make it right. However, this is going on in every town, it just doesnt make the news. It is a sign of a much larger social/cultural problem which is rapidly developing.