Might be prison justice inflicted by other prisoners, but in my experience with prisoners, unless it's a gang thing or a random prison scuffle thing, they usually only go after guys who have sexually abused and/or killed children. Guys who have committed crimes against children are always fair game, and are therefore usually held in segregation.
Who knows though? Might be a guard. Might be a suicide. Might to a result of an unknown scuffle with a fellow prisoner.
Either way, I don't think many will shed tears.