That is, of course, up to you, but, what you are saying is that you are making an off the cuff statement and not placing a whole bunch of bummer on the event. Just a matter of fact, yea, that actor died. He doesn't know them personally, only as characters. If it were a grandparent, aunt, uncle, cousin, parent or someone that he is emotionally close to that is different. Based on his age, Carrie Fisher is an old time star. He only knows her as Princess Leia. So to him Princess Leia has died, just like Hans Solo did in the last movie. I'm just saying what I'd do, you know him better then I do.. so go with your instinct about it. I just don't see the necessity to say anything unless he asks. Otherwise, you add drama to the situation and he might react worse to the drama then the actual news.