Stay with them in that journey to the hard place and their walk to the other side of the hurt. Ultimately physical and emotional healing is an internal process. Young people need company on that emotional journey to healing. I also have a concern about some things I am hearing from people saying that this sort of thing started when the right to punish kids was taken away from parents. When my kid does something wrong I spanked them and if that meant a few welts on his legs so be it.
Corporal punishment is the perfect model of violence before thinking.
What our kids need are models of thinking before violence. I am the first to say that it is hard to keep thinking when your child has aggravated you to the edge of anger, but it is crucial. Children do as you do, not as you say. We can talk about ending violence all day and night but if we don't walk our talk everyday, in our homes, we will not teach anyone anything except that we are hypocrites. We need the kind of support that understands when we make mistakes and helps us to correct them.