If you are replaying a death scene that you witnessed yourself in your mind, this is natural. You are just sad about what happened, a traumatic event that you were unable to prevent no matter how hard you tried. You are probably sitting there brooding over what you could have done to have stopped the horrible event from happening when the truth all along was there was nothing you ever could have done. You were ruined from the start and there is nothing you can do about it now. You need not worry about an event which you could not have prevented. Just look past it and try not to replay the worst events of it.
If you have a dream of a dead man then this means that you are worried about your health. The man represents you and you think that if you don't stop a certain behavior soon that you might end up like him. A dream like this occurs when death is on your mind. Perhaps you routinely overeat and you just had a heat spasm and are now thinking about how this behavior could lead to your early demise. Maybe you have just taken up smoking ad are worried about how it might affect your health. Maybe your drinking is taking hold of you and you are finally starting to feel the damage that could be caused by it right in your liver.