Preface: I've had a lot of experience with death (unfortunately), 1990 was a bad year (5), also have lost 5 more family since then, and 3 friends. So these are my thoughts...
If you want to write about death and dying authentically then there's a lot of things you can do. My experience and the stuff below is death of a loved one. Death of a stranger or enemy is different again.
Writing about death is not so much about the dead person, as the people around them, generally. There can be some powerful stories about a dying person - The Fountain, jumps out at me straight away. But also there's other films (I remember one with Mary Tyler Moore in it that was exceptional, but quite a while ago).
Elizabeth Kubler Ross "On Death and Dying" suggested that there are 5 stages of grieving, but how people go through them are individual.
Stages are:
1. Denial. This can be the 'Oh no I can't believe he's dead', or feeling that frisson of excitement and panic everytime you see someone like them on the street. Or indeed having an overwhelming feeling that they're not dead, they're hiding.
2. Anger - This can be blame towards the dead person, towards whoever they think is responsible for the death, to God/Universe, the neighbour's cat. Whatever. A big one - is blaming themselves.
3. Negotiation - to be frank, I don't see how this one turns up in grief at all. Dying, yes.
4. Depression. Mourning the loss. Tears in unexpected places. Not feeling like there's any point to life now that the loved one is gone. Depression is not just a feeling, it's also about having emotional room for things. So happy events can be stressful simply because it takes too much out of one. It can also be a reminder of what is lost. It's knowing you've read the last chapter of their book.
5. Acceptance. They've gone. You move on. Your life takes a new shape and you live with it. You remember them with fondness.
None of these stages are the be-all and end-all. You can go through each of them at different times and multiple times. Some you can skip entirely. Some you get stuck in. Some can run concurrently with each other.
There's also the anniversaries - death anniversaries, anniversaries of important events. They can cause extra problems for the grievers. And the body remembers when the mind doesn't. So for many people there is a feeling of sadness and depression on the anniversaries even when you've forgotten the dates. The depression lifts when you remember that it's an anniversary. There also is a lessening with each anniversary - 7 years appears to be a magical number for that, if a person has grieved well.
So.
Decide on the type of death. How the death happens, will affect what you need to write about: Sudden or due to illness or due to a risky situation.
If it's a
death by surprise (i.e. sudden, unexpected), it will have the consequences of someone just not being there. No preparation, just the shock of the news.
There isn't just the grieving, and the feelings of sadness. There's also the whole world-out-of-kilter feeling. The panic while you try to find some sense, there's been no preparation.
The denial phase tends to occur longer, simply because there was no preparation. They're here, they're gone. It's a huge shock.
Different people deal with that feeling, in different ways. And depending on how connected to the dead person they are.
Some people will fight to try and return their life to their pre-ROS rhythms. Others will find new ways of living without the dead person.
Death by Illness will have a pre-grieving time. This is where the stages that Kubler Ross has makes most sense. Not just for the person dying, but for those around them. And definitely negotiation becomes a step. "Live long enough to do this or that". Live until Christmas, that wedding, seeing an absent loved one, just one more time. There's also the worry and dread of what the grievers will do once the person is gone. If the relationship has been dysfunctional at all, there'll be a guilt at the feeling of relief, or a regret on not being able to mend fences. There's lots of time to worry about once they're dead, as well as deal with the extra demands both emotional and physical that someone with a serious illness. Your emotional space shrinks. Also another thing to consider is that people will transfer worry about things they can't control (the person dying) into things that they can - like money, work, etc.
The other thing that happens with a dying person - is their deconstructing life into what is important. Remembering old memories, and pulling out the things they've learned. It can be like a re-cap.
Death due to a risky situation is different again. It's similiar to both of the above, because no matter how much you know that they are taking a risk - there's a part that just doesn't believe that they'll die. On the other hand - there's always a bit of preparation before hand, a bit of mindset dealing. Knowing that this time might be the last that you see them - tears at the good bye, having a way of dealing with life that doesn't include them.
Laura's episode in LH with Amelia and her mum while the dad is off at war, is a good example of this. Amelia deals with the risky situation by not thinking about it. Amelia's mum takes comfort in the ways she's prepared in her mind for her husband's possible death. They are both different ways of coping.
Once they've died there's the dread and sadness of knowing that what they were afraid of, has come true. That can lead to avoiding risks themselves later.
The other thing to remember, is how close and attached a person was to the dead person, will affect the intensity of how these things. The less attached, the less it will be an interruption in their life rhythms. eg. Princess Diana and the world vs Someone and their mum.
Anyways - before this becomes a novel in itself.
I hope there are lots of ideas in there for you.