I am sorry you had to deal with such a sad situation. But you are to be commended for how you handled it. It's hard to believe how detached, clinical, and self-serving people can be, even about their own flesh and blood. My dad has stories like that, from emergency calls he went out on as a fireman. He told me a story about a man who had a massive heart attack and dropped dead, and how the man's son was literally stepping over his father's body while on the phone with a lawyer to begin estate proceedings. I just can't fathom how people can be like that.
You did your friend a great service and tried to be his advocate when he could not be his own. Do you know what will be done with his cat? I think if you or coworkers could help find the cat a good home that would be something your friend would like.