Sudden rabbit death?

I'm most shocked and grieved but I still can't understand what caused his sudden death. Moments before his death he was lying on the floor just beside my bed, then he got up to roam, got under my bed, I heard 2 loud bangs like he had hit himself on the roof of the bed just after that I heard his scream, I jumped down to check and found him lying on the floor, eyes open, very still and not breathing. I called my father and told him to come asap, but it still took him 30 minutes to come and meanwhile I put him on my bed, he was really elastic, his head was rolling around, eyes wide and he still wasn't breathing, I got really scared and at that moment I knew he was dead, I really regret not checking his heartbeat though. My father thinks he died from a heat stroke, the temps were very high lately, today was like 43c in here and from a week he was very lethargic and having the hard breaths he usually had in summers so I didn't really thought of a heat stroke possibility, I did keep his water bowl filled with chilled water and some ice cubes in a bowl for him to lick, minutes before his death I even sprayed him with ice cold water to keep him cool but he never drank his water more than usual or ever licked the cubes. I still don't know what killed him, did he hit his head while under the head or did he died from a heat stroke?? he did displayed heat stroke symptoms I read online but why did he only die moments after going under the bed??? The scream & bangs?? We buried him 4 hours after that incident, I've read online some people's rabbit going very still to a point of making owner think of them as dead then becoming alive again, do you think he could still be alive? we didn't took him to vet because we thought him dead since he wasn't breathing, he never breathed in 4 hours, he was dead right? I even fear to think we buried him alive, I wouldn't imagine something like that even for a nightmare (


Rest in peace my angel Nonu 2009-2016

Yes, he was dead there is no question about it. It's true that rabbits can fake death when put on their back but they are still breathing (just in a very quiet slow way) and it doesn't last for 4 hours.
The hitting his head was probably the adrenaline rush before dying - it's not rare for a rabbit to run or trash seconds before passing, it happened to one of mine too.
For what killed your bunny, we can't tell for sure without an autopsy. Your rabbit wasn't that young (vets begin to refer to rabbits as "senior" past their 6th year) and it's true that rabbits don't like the heat much. It's possible that your rabbit wasn't able to handle it as well as he did when he was younger. It could be an hemorrhage, a heartstroke or it's possible that he had a cancer or something that you didn't know about. Sudden deaths like that are awful for the owner because you didn't have any time to "prepare" yourself. On the other hand, if your bunny was acting normal until his death it's very probable that he wasn't in pain before, and his death was very quick so he didn't suffer much. Still, I'm very sorry for your loss.

Sorry for your loss. Heat can be a factor, but, have had some pass that were not showing any symptoms, so it's hard to say.