bet he's kicking himself for driving too fast.

Bet he's not.

NA he is relaxed cause he knows that he is gonna be chilling on a wheelchair for the rest of his LIFE!!!!!

suicide bombing gone wrong?

He is calm because the receptors in his legs are sending pain signals to the brain through the nerves and then the brain kicks into defensive mode and releases endorphines, (Which are like Our Brain's secret drug stash), and this calms the body.
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Also when too many nerves are damaged at once the pain receptors can overload the brain and it shuts down momentarily to limit the amount of trauma....(Pass Out or go Numb)...it's also called "Going Into Shock'.
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Either way, he won't be dancing for a while.

oh shit my legs gone... woooow i can see the fucking bone! lol..

just a little scratch just walk it off, wait he cant HAHAHA