And he should get the kind of safety I've seen on treadmills. You fasten a wire to your shirt, and plug the tab on the other end into the control panel. If the tab pops out, the treadmill stops immediately.
That said, I'm not sure why the incident caused so much lingering pain.
Also, is the treadmill in the house?
And like most people, when I say "All I can say," it naturally turns out not to be all I can say.