Donkey spontaneously combusted

I had a donkey and while working upstairs I had a notification come up,  pretty much saying my donkey had died from burning alive.

I quickly ran downstairs into my farm and there, to my surprise, in a patch of flame was my donkey dead,  just his saddle and chest left behind, then to my surprise my horse that lived with my donkey was on fire!! Shining with full diamond armour the red glow of the firey flames overcame my Jimmy, my wonderful speedy loyal horse 🐎, he perished leaving his saddle, diamond armour and some leather to remember him by.

I stood in shock!! What had happened, how did they go on fire?! I checked around the area no fire nearby, no campfires, no lava, no flint and steel and no magma blocks to be seen, so I dug down and around the area but still, nope, nought, nothing that could have done this!! All that I could do was set up a memorial for my two loyal steeds....

Well my issue is that where my donkey and horse lived harmoniously together there was absolutely nothing in the area that could have ignited my donkey to burst into flames. I don't know if this is a bug or glitch but any ideas of how this could have happened is welcome, may just be able to give me a bit of closure to this tragedy.