Wow, very sad!
I recently wrote a character with survivor’s guilt for a very different situation, but it was a very new and interesting experience for me. Actually, it took me a while to realize that he even had it, funnily enough. When I was writing scenes in which he was involved, or writing chapters from his perspective, everything came out a lot angrier and more intense than I expected. Halfway through the story, I finally realized that he was lashing out due to his grief and pain.
That doesn’t mean that is what survivor’s guilt always looks like, however. In fact, I think that guilt and grief can be tied very well together, and look very similar. But the reaction shown is going to differ depending on the character. For my character, a strong-willed person with a bit of a temper already and a lot of bitterness, anger was a natural reaction to what he was feeling. To him, he was angry that this terrible thing happened, and that he lost so much because of it, and that now he had to keep on living with all that loss when it might have been easier to just die along with his friends.
If you are familiar with the stages of grief:
A lot of those emotions and symptoms are very applicable to survivor’s guilt. Emotional outbursts, panic, denial, shock, anger, as well as parts of the recovery can all be a part of what they are dealing with.
Think specifically about your character, and what makes the most sense for them. They may not go through every point on the graph. Maybe, if they are a quieter type of person, they just feel numbness, or denial, or despair. Maybe, if they are more tempestuous like my character was, they lash out. Perhaps they feel panic, or get paranoid and put up extreme precautions to ensure that nothing like that ever happens again, to the point where things get a little out of control. Maybe they blame themselves, feeling a lot of self-hatred or going over the scene over and over in their minds and trying to figure out what they could have done differently.
Even though your character’s killing of this person was unwilling, they may still blame themselves, or think “I should have been stronger/better/smarter” etc, or think “If I have done this differently, then we never would have been in this situation”, even if realistically there was no way of knowing what was going to happen.
Another common reaction is the “It should have been me” reaction. The survivor may feel that the person or people who died were better people than themselves, or that they had more to live for, or even that their actions were what got them into trouble in the first place and that they should have paid the price.
Remember that their guilt will tell them to think terrible things, even if they aren’t true and aren’t realistic. The mind will go to great lengths to blame itself when it is entrenched in such terrible levels of despair- even if there was logically nothing they could have done, guilt will always tell them that they should have done better.
Another thing to remember is that they will likely be experiencing grief at the same time. After all, they just lost someone close to them. That is an entire presence that will be forever missing from their lives, and to make it worse, they feel like it’s their fault. It’s okay if sometimes they just miss this person, and that’s enough to deal with.
Finally, don’t neglect the recovery side of the graph. With support, your character can learn to cope with what happened. Any one of the things listed above can be catalysts for a new phase for your character, emotionally. For my character, it was reassurance and support from his friends, particularly the introduction of a new character, who had a very positive influence. Your character may still carry the loss and the guilt with them, but it was will someday be a lighter burden.