Ok, here is how I read the tealeaves:
The top of the broken piston is shiny, the others are dull. The broken piston has valve head marks in its top, And you have a broken cam, bent pushrod, and a broken connecting rod.
How about this for a scenario: Antifreeze has been leaking into the cylinder for some time, evidenced by the shiny piston, and during one of your starts, you briefly hydro locked the engine seriously stressing the connecting rod.
Then on the fateful day, you went tooling down the road at 2600RPM, and the weakened rod/cap let go, and batted the piston up to the top of the cylinder where it stopped. As the engine continued to turn, the valves went through a few cycles, and left their marks on the piston top, bent the push rod, and broke the cam.
Thoughts?
-Chuck