Work makes me super anxious rant

I take medication for anxiety but lately it seems like it hasn’t been working well. I work at Fred meyers (Kroger for those of you who don’t have them in your state) and a couple weeks ago there was a shooting at one of the Fred Meyers in Washington state, I don’t live in Washington but I live in Oregon and I get so much anxiety that there may be a mass shooting at my store, I always think of my escape route while working, sometimes people come in wearing all black or with dark sunglasses and I get super bad panic to the point where I feel like I need to run away and hide. I’m a cashier so it’s not like I can avoid people and I feel like quitting my job due to the stress.