I'm going to give you want the other family no doubt would if they could. Compassion.
My sister was killed at 17 by a drunk driver who on top of everything else, was driving with no headlights on. She hit him in the driver's side door. Her car flipped upside down and landed on top of his car. His car then careened off into a cornfield. They all (4 in total) laid there for hours before anyone found them.
She died 4 days later in the local ICU after having already having had brain surgery as a Jane Doe.
Never, not once, was I ever pissed off at the other driver. I was too grief-stricken and overwhelmed with taking care of my mother who had, rightfully so, turned into a basket case to be pissed at anyone.
Anyone other than myself. I was supposed to have gone home that weekend but something came up so I didn't make the trip. So I blamed myself. If only. If only I had gone back home as I thought about doing. If only. Then she'd have been at home playing with her little nephew instead of out on the road at night.
No one can forgive you but you, babe. He was 70. He lived his life. If God hadn't meant for him to go then He wouldn't have called him home. Whether you believe in God or not He believes in you and loves you just the way you are.
Find some peace in that loved one.