I'm sorry you are still struggling with this tragic event. I can't honestly say I can relate to what you experienced. But many years ago I worked in the emergency departments of two different hospitals (plus a stint in the O.R. of a third. So I saw, & dealt with, my fair share of death. Some of the images still come back to me from time-to-time all these many decades later. I'm not a mental health professional. But personally I would say what you've been experiencing certainly could qualify as PTSD.

Here are links to 4 articles, from PC's archives, that (hopefully) may be of at least some small bit of help:

Posttraumatic Stress Disorder (PTSD) | Psych Central

Coping with Obsessive Thoughts

Understanding and Coping with Emotional Flashbacks

Letting Go of the Past: Why Memories Remain Painful Over Time

Best wishes...