The deceased was 16, certainly old enough to realize that when you threaten someone with deadly force, they might well kill you. His family is to blame for not teaching him that bad actions have bad consequences, but the deceased held up a citizen and died. His actions alone led to his death.
If he is old enough to stomp a grown man and put a plate in his jaw he is old enough to die. The pizza guy may lose his job but he is walking around whole.