Eric F said:
tunnel vision blinded me so much I could not even get a visual of the first shooter I saw. How can this be prevented?
Experience and training.
Now you have some experience.
Most folks aren't really ready to deal with these situations the first time it happens to them. A few people have commented that you panicked, but assuming you have no LE/Military experience, and have never been exposed to combat, what should they expect?
It wasn't your fight, and you did well enough to survive it.
For training, I Do suggest you visualize these things in your head from time-to-time, and create little "what-if" scenarios and imagine the solution. I call it "occupational-paranoia", but every time I walk into a bank/store/restaraunt/etc I find myself planning for a fight... It isn't obvious, and it isn't like I'm openly paranoid. But, I look around and I think "cover, concealment, exit, backdrop, etc". I've been doing things this way for years, and it makes you more mentally prepared if something does happen while you are in that situation.
PLEASE NOTE: It will never happen exactly the way you imagined it will... But the more "solutions" you've thought of, the more likely you'll be to act in a manner that saves your life.
Anyway, that is just one way that you can train your mind to overcome the shock of a deadly force encounter.
The actual experience can only be gained from being in those unfortunate situations. Put simply, short of the military/LE guys, you now probably have more experience than 90% of the people on this site. It may have only been one event, but outside of military/LE, how many folks do you think have actually dealt with what you did?
You did fine, because you survived. Learn from your own mistakes (it sounds like you have), and make a mental game plan for future incidents.