But know that he is in a better place. If you believe that the Celestial kingdom is anything like the scriptures suggest then he is in a much better place than all of us.
I know it is not what you wanted and what your son wanted either but at the same time I am certain that your son still loves you and would want you to forgive yourself.
I am sure your heavenly son still loves you and knows / understands that it was an accident.