I am very sorry to hear about your son.
My husband's elderly aunt died a few days ago. She was sitting with her daughter and praying. Suddenly, she called out, "Joe, Joe" and died shortly thereafter. Her brother Joe died about ten years ago.
Another lady I know called out the name of her departed husband right before she died. She reached out her arms to him.
Thank you. I have heard of people calling the name of a dead relative just before dying too. I find that extremely comforting.