Wikipedia (yeah, I know) indicates that there were autopsies on all three victims, showing that they “died upon impact”. I’m not sure if the article is correct, as I remember hearing that as soon as they recovered the bodies from the wreckage, they were immediately buried at sea. For what it’s worth, here’s the Wikipedia link: https://en.wikipedia.org/wiki/John_F._Kennedy_Jr._plane_crash
It’s news to me that there were autopsies. All I previously knew was that the bodies were cremated, and then carried back out to sea and the ashes scattered.