This happened during the Chechen wars in Russia, if I remember correctly this specifically happened during the second one.
Supposedly, both the victims and the killers were identified (I don't remember their names).

The perpetrators were 16 year old Chechen teenagers members of the Chechen terrorists. All of them were identified and arrested, some are still in prison and some died while serving their sentences.

A friendly reminder that youth is not "dumb" but simply inexperienced. Young people are perfectly capable of committing atrocities that even adults would not think of. The case of Junko Furuta is another example of this, these " kids" (I put kids in quotes because a teenager should in no way be categorized as a child unless he or she is a very young one) are as evil as an adult can be.

If this doesn't prove that it should be a universal law that teenagers who commit crimes should be tried as adults, then I don't know what will.