Son said there was some antifreeze in it, enough to be slushy. He didn't start it. One of my hot rod buddies advised to have it towed to a garage and let it warm up and have them inspect it tomorrow.
Son is 20 and learning the hard way. I asked him back in the fall if he checked his antifreeze? He said yep in a disgusted way. I asked him today what changed since then? He said "nothing I guess". Probably won't be the last time he doesn't listen, but, I hope he starts to learn that I'm really trying to help.

Hopefully there is no real damage.