Hopefully some good has come out of this and we all triple check to make sure things are secure before we crawl under a vehicle. I know I'm hesitant to get under a vehicle now unless it has 2 sets of jackstands holding it up.
x2
If you've got a manual tranny car, also MAKE SURE you disconnect the battery if it's up on jackstands.... shorting the starter solenoid against anything can cause the vehicle to rock off of the stands if the car is in gear!
RIP, Dave...