Going back after a shooting

There was a shooting at the mall I work at. I was on lockdown in the store completely by myself for over 2 hours until a cop came to escort me out. I had multiple panic attacks and almost passed out. Granted, it was a retaliation/fight and not a mass shooting which I’m EXTREMELY thankful for.

However I still hear hear those gunshots and the people screaming in my head. I feel like I shouldn’t be stressing out over this as much as I am because people have gone through much worse, like actual mass shootings.

How do you go back to work after something like this? I’m lucky I have the next few days off, but I’m terrified of stepping anywhere near that place now.