Can bad set timing cause valves to break and destroy head and pistons?

put in rebuilt heads on a 2002 ford f150 4.6 v8. I think the timing chain was put on wrong but not sure. Upon starting car ther was 2 loud knocks. The engine did not turn. Open the heads again and three of the four valves had completely broken with enough force to send 1 valve through a piston an d made a hole. Pistons were damaged and head beyond repair. What could have happened? Any advice would help. THank you