My father had the same thing.
All of a sudden his BP started dropping and he felt like he couldn’t move or breathe.
He underwent many hours of surgery and they repaired his aorta. Basically what happened is that it sprang a leak/tear.
He is fine now.
Wow. Good luck and blessings on your dad. Torn aorta is usually fatal...over 90% I hear. R Holbrooke had world’s best medical care and he did not come though