So when my mom got up this morning there was a dead frozen solid rabbit in our fenced in back yard

There were no marks or wounds on it. My dad lets the three youngest out to go to the bathroom between 4am and 5am before he goes to work but there is no way that they could have killed it and then it froze solid by 8am. My mom said when she was taking care of it that the 3 youngest really didn’t care about it and that it didn’t appear to have a broken neck or anything so I have no idea what happened.