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."