Assuming no rocks or ice in the center, I assume childish play or harmless prank when the target is another child or a healthy adult of sound mind.
Rocks or ice? Different ball of wax. Mentally handicapped or physically handicapped individual? Different story.
A person of sound mind would laugh it off and throw a snowball back at the kids.
Obviously when I was growing up there were plenty of people who were not of sound mind according to you.
One just did not throw snowballs at adults unless permitted to do so, either by the adult joining in or the adult's past joining, and even that sometimes didn't work.