I can only speak for how the law does things from what I know.
You can charged with first degree murder, if it can be shown that you formulated the intent to kill. Even if that intent was formulated just a few seconds prior to your act.
Second-degree degree means that you didn’t care if your actions would kill, but you did not formulate the intent in itself. You just didn’t care.
In Nevada, this offense would probably be second degree murder. The actions of the kids ensured that he would die, even though the probably only wanted him seriously hurt. But Nevada recognizes a murder charge if the outcome is death, regardless of your intent.
Second degree murder can carry the penalty of 25 years in prison. For many of them, that’s a life sentence because they will have no meaningful life and productivity after they get out. This is assuming that any of them had a future to begin with.
Fair enough, but from where I sit, kicking someone in the head demonstrates the requisite malice aforethought. Can be a fraction of a second, doesn’t even need to be a “few seconds”. What’s the accidental explanation of that? “I just meant to break his nose, not to crush his skull?” I don’t that would work for you, or me.
Anyway, intent almost always has to be inferred. There have been cases where a killer admits the intent to kill, but that’s not the norm.
Of course that’s all theoretical in this case. If they’re charged at all, it will be some lesser homicide, but that’s due to political, not legal, considerations.