My Mother died several years ago. She was a very difficult person. This left me with strong mixed feelings.
What do you say to a person who has strong mixed feelings about their Mother when she dies? They still need assurance. The assurance that you care, whatever. They feel very confused and unable to sort out their feelings. They likely have some guilt feelings over things that were said or done and which are now beyond resolution. They probably wish that they had been able to resolve things better before she died. They feel hung up because now there is no more resolution possible.
On one hand my Mom was my Mom and she had given me life and brought me through many years, even though she wasn't perfect. There was a lot of attachment there. As I approached my teen years she became less loving and rather critical. My sister had always been her favorite child. As an adult we would get into angry arguments. Sometimes it seems she deliberately caused these.
What can you do?
1. Assure him you care.
2. Offer to be a listening ear. Let him talk things out. This will help him think things through.