There have been some teens that ended up being the perps in these cases. The young girl, last seen, riding her bike around her apt. complex, an artist's compound, in Santa Cruz, Ca. ---and a police officer saw a teen dumping his trash ---they found the child's body in the dumpster.

I think her name was Hannah?
And the teen who was arrested for assaulting and killing a 5 yr old neighbor girl that he had befriended---and he dumped her in the woods behind their complex. I think he is still awaiting trial as they have to test him for mental competency ...last I heard. They became suspicious of him because he kept stalling about offering his DNA, like all the other residents in the neighbourhood agreed to do voluntarily.
Another recent one was in the UK--Irish coast, I believe. A 6 yr old child was taken out of her bed while her parents were sleeping---and murdered. A 16 yr old neighbour who had previously bought pot from someone in her family was arrested for her murder. I think he snuck in to steal drugs or cash but found the sleeping child and took her?
And of course that crazy guy who snuck in, and was video recorded as he kidnapped a sleeping boy, while his twin brother slept next to him. So horrifying.
Teens can be quite evil and brutal.
ETA: Just saw another post and recognised the names of the examples I was giving. Old age has made it hard to retrieve names from my memory banks these days.]
[Madyson Middleton, Jenise Wright, Alanna Gallagher]