Worst nightmare.
I always tell concerned friends about some study I read where randomly getting hit from behind is the
#1 fear of all cyclists but is statistically rare. The actual
#1 cause of accidents is cyclists taking some action based on the incorrect assumption that drivers see them. Who knows if that study was meaningful or not, but it's just awful to hear about somebody getting hit from behind. I hope there's no serious physical damage.
(BTW I'd call that a KO, not a TKO
)