Tragic situation.
My guess is that the guy was in a hurry, tired, and needed to get the work done. People make mistakes, we can thank this guy for helping to remind the rest of us, don't cut corners when it comes to safety, you might not have a "next time" to get lucky.
I always use jack stands, and leave the floor jack at another lift point lowered just below the point of contact. As a safety back up.