His caliper had come off.

The Theory:
One bolt came out or broke off (sorry, I did not look closely enough to see). Then, all the stress of the braking action over stressed the caliber's eyelet around the one bolt remaining - and the caliper fractured.

What I did:
I got some solid number 10 (or 12?) ground wire from Fontana Maintenance and hung the caliper from an exhaust hanger.

The wheel was marred up some from the caliper falling off - but no real damage was done. He limped home with three wheel brakes.