If you compress and melt the snow on the outside the ball becomes like ice and can do a lot of damage.
There was nothing in the article to indicate it was anything but a snowball. Do you have insider information?
That is snow between 28 to 34 degrees. Never did any property damage to vehicles. This was normal teen and pre-teen behavior in Wisconsin in the 1970,80’s and 90’s. My kids did it and got caught once, the officer brought them home and gave them all a strong warning. I got his wink and caught his laugh as he left. You’re just looking for an issue. Boys will be boys. We sure as he** were not using guns. But back then I brought a gun to school and put it in my locker so I could go squirrel hunting with friends. No one blinked an eye. Squirrel is good fried in butter with taters, onions and carrots. The dogs loved the squirrel heads.