Witnessed horrific violent accident 6 years ago, still full of rage

Hello. I witnessed a horrific violent accident resulting in the death of a 2 year old boy. About 6 years ago. Now, I am extremely pissed off all the time. When my neighbors make noise, it makes me want to go downstairs and scream at them and fight them. (I am not going to do this.)

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I need help explaining to my loved ones why I feel this way. My partner keeps questioning me and asking "Why do you feel that way?" as if she is trying to prove that my feelings are "illogical" or something. It is overwhelming me. Of course I don't want to explode in rage at her, so I just walked away because she is not willing to listen.

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Can someone give me any resources on explaining why victims of this type of PTSD feel like they need to defend themselves physically even when they really don't/shouldn't? I just want her to stop being so unfeeling to me. I isolate myself when I'm acting scary; I do all the right things; I'm on meds and want to start EMDR therapy. I just want the people I love to understand and stop acting like there's something "wrong" with me. Obviously there is something wrong with me, but it's not my fault. I'm fucked up somehow and I would never have chosen this. I hate being this angry, it is not something I do for pleasure.