The only way a key will give way if it has suddenly stopped while the belt was trying to shift it.
Tension could have been low and causing all valves to bent putting some force onto the key while the engine is turning over.
If the bolt wasn't tight. It won't cause that.

 

Good advice Paulyy. I got the cam gear off and in the process, the end of the camshaft came with it. Guess I know what to buy next. Camshaft assembly, gear, and box here I come..