my timing belt broke

What is your question?

I was at a stop light and my car suddenly turned off i tryed to start it twice and it did not start so i pushed it to the side waited for a tow truck and whil i was waiting a man came by and tryed to help me he had asked me what happened and i told him, he then pulled off my oil cap and asked me to start the car i tried to start it and it did not start he told me it was my timing belt because the valves where not moving can that be thrue and if so how will i know if there was any damage to the valves and any thing else.