I personally cannot relate to seeing something horrific, but my brother (second brother) and my mother did. About 10 years ago, my mom brought dinner to her brother. He was depressed and living alone in a big house after his recent divorce. She walked in because he did not come to the door. She thought he had a red hankerchief over his face, but he had shot himself. My brother, five years ago, had his 8 yo son hit and instantly killed by a car right in front of his house. He was out there within minutes of the accident. On top of that he grieved because his son had asked him right before the accident to play catch with the football with him. My brother said, in a minute, I have to finish the deck.
I just lost my father 6/6. He was sick for a long time, but the last few months were really difficult. A month before he died we found out he had a brain tumor on top of his other health problems (copd, diabetes, high blood pressure, and lower lumbar stenosis). Add to this the loss of my oldest brother (first brother), three years ago to cancer and we've got major grief.
The way you deal with grief totally depends on how it happened. With my dad, even though we are glad he is no longer suffering, he was my dad. The most special person in the world to me besides my mom. My nephew was only 8 and died tragically. That was more unacceptable than my dad's passing. My brother also was no longer suffering.
I realize that knowing people have experienced somewhat what you did does not make it any easier to grieve. It does help to know that it is unfortunately all too common. We all have to go sometime. We have to depend on God to know that all things will be okay in the end. Find strength in Him. I am not preaching as I do not know your faith, I am just saying that we cannot handle the amount of grief we feel alone. You cannot talk about what happened and that is a huge burden to carry alone.
If you open the door even a little bit - the devil will fling it open. Keep it closed with prayer.