You're being quite vague so I'm limited for types of responses to offer.

I think processing this in therapy might be your best option to deal with the guilt, and maybe send him an email or letter, saying what you could not say 2 years ago.

It might not provide the type of closure you crave, and you will probably have to create your own closure, but at least you will release the pent up expression that's been weighing on your psyche.