There are certain extremist groups with Christianity and Judaism that have codified their endorsement of violence to achieve their theologically driven objectives. At this particular point in history, those are quite small subsets of those larger religious traditions, but Christianity in particular once had a widespread devotion to violence as a means of extending its influence. Islam can change too, but we can help or hinder the pace of that change, by our choices in how we treat moderate and liberal Muslims -- the more we alienate the moderates and liberals, the more susceptible they become to the welcoming advances of the extremists. Personally, I don't want to help the extremists in any way.
Until we know more about this particular family and young man, I think it's important to keep in mind that "Muslim" is just the default religious identity of the entire Bosnian ethnic group, and the fact that a Bosnian identifies him/herself as "Muslim" when asked what his/her religious affiliation is, doesn't imply any serious level of belief in the teachings of the Bosnian brand of Islam (which is a notably non-extremism-prone brand to begin with). It's sort of like asking a native Englishman what religion he is -- if he doesn't give a whit one way or the other about religion, and hasn't been to church in years except to attend a few weddings and funerals of friends and relatives, he'll generally say "Anglican" -- but trying to make a connection between Anglican theology and any particular acts of this individual (good or bad) would be groundless.
No, there are not. I can claim to be a major league ball player but my claim has nothing to do with professional baseball.
Islam can not divorce itself from violence without becoming something else. Christianity used violence in spite of it's universally accepted doctrines, not because of them. "Moderate" muslims can't denounce the extremists because they don't have a doctrinal leg to stand on.
Would it be groundless to entertain the idea a man may be Catholic if he makes the sign of the cross before and after short periods of silence?