I would say that it would be best if you approached their parents if you know them. I understand that the sight of a deal squirrel can be quite unpleasant, however, teens can behave like this sometimes. This behaviour does not necessarily mean that they are dangerous or that you should have more reasons for concenrs. However, they do need boundaries and the ebst people to enfource them would be their parents. If despite yoru efforts, they continue killing animals, you could call your local animal welfare centre or organisation that deals with animal protection.
Hope this helps
All the best