my view is the chain jumped a tooth and the valves hit the pistons thus breaking the followers.
I would say the pistons will be damaged and another engine is the only option.
tell him straight, he's better off selling the car 'as is' or paying a garage to fit a new engine and have a warranty, harsh but true :roll:
none of the above is your fault, it's a common problem on the early z22se engines, the fact it was noisy when he stopped driving it confirms to me the chain had already begun the destruction :roll: