How sever is a mob action warrant charge

How sever is a mob action warrant charge?? A friend of mine was involved in a incident with one of his friends from Illinois where my friend is not from he lives in michigan . His friend had gotten into a fight it is now months past when it all happen a detective had called my friend an was interviewing him for the case because of the other person involved was injured my friend was just called again by a detective an was told he now has a warrant issued for his arrest for mob action because all he did was try to get his friend from fighting an ran from the incident after the fight was done so Illinois issued a warrant for him for mob action an he lives in michigan he wonder how bad it could be for him when he turns him self in any info would be very much helpful thank you .