Pretty much the definition of "worst case scenario."
Warning: Do not watch if you're in the middle of a skydive.
Let me tell you something: I am not a particularly brave or adventurous person. So, for me, a run-of-the-mill, uneventful skydiving jump would be the single most terrifying life experience. So, just reading this skydiver's account of how he had a seizure shortly after jumping out of a plane two miles up in the sky reduces me to a puddle of quivering goo:
"Possibly the scariest moment of my life. On the 14th of November 2014 while doing stage five of my Accelerated Free Fall program I have a near death experience. At around 9000ft I have a seizure while attempting a left hand turn. I then spend the next 30 seconds in free fall unconscious."
Luckily, this guy's jumpmaster was able to swim through midair in order to reach him and pull his ripcord when he was still at 4000 feet. Still, he ended up falling another 1000 feet before ultimately regaining consciousness managing to land safely (and softly) on terra firma.