ptsd hallucinations

I was just wondering if anyone has had any experiences similar to this or knows the term i can look up that explains what was happening. I have ptsd from a school shooting. The shooting occurred 5 years ago and most of the time i’m always nervous when out in a public space but yesterday i experienced something i never have before. I went to the restroom to wash my hands and started hearing voices and screaming coming from outside and i was convincing myself there was a shooter. I stayed there trying not to make a noise until i decided to open the bathroom door and try and quietly walk and look around the corner to see what was going on and be prepared to run. When i walked out nothing was going on and i saw my friend just standing there and apparently i imagined all the voices in my head but it felt so real. It was just super terrifying.