I have a 2010 Prius, and according to the manual, this is precisely what happens if you push the power button while moving.

2013 Prius here. So, I tried it on the way home. A quick push of the button is ignored, but if I hold it down the car shuts off. It takes power steering with it though, so I don't recommend it under uncontrolled circumstances. I had to come to a stop to restart as well.

Of course, if the computer is busted, I'm assuming the long button press will be sent to /dev/null.

> It takes power steering with it though,

That is what sucks about cars with power steering, they don't get any of the benefit a car built with no power steering does.

I had my old Caravan chew threw a serpentine belt once...

Getting that boat of a minivan around the next corner in traffic was both entertaining, dangerous, and probably the best upper-body workout I got that year.