I know you pain since my wife passed. You will need support as I know this is so hard for you however not taking anything away from your pain your father is going to need more than one can imagine and you will have to be a big part of that. Be strong for yourself and your father. Grieving does it's own thing and sometimes it controls you. As Doc says it best "Grieve the way your grief dictates" The tears will roll down your face and let them as they are rolling down mine now. God bless you, your father and the entire family. Nothing more I can say will help your pain and sorrow except to take each minute, hour, and day as they come and gain a small amount of strength from each.