Nothing wrong with that from where I sit.
So here's one for you:
You are at the mall with your significant other and a loon with an AR-15 bursts in and starts blasting.
"Down!" you tell your SO, whereupon you draw your concealed snubby, step out into the corridor, and yell, "Hey, Asshole!"
The shooter spins, and you cook one off, hit him right between the eyes, and he goes down, dead.
Fast forward to, you in the back of the convertible next to the beauty queen as the city showers you with confetti at the parade held in your honor ...
Every bit as much a fantasy as hopping into your spaceship and rocketing off to fight the Evil Empire, whether you know it or not.
Go read some of Rory Miller's stuff. Talk to guys who have seen the elephant and had bullets flying at them. The fantasy is fun. The reality is maybe not so much so.
Ask anybody who knows about real deadly violence what is wrong with that shootout at the mall scenario. When they stop laughing, maybe they'll tell you ...
Not to say we don't have heroes, nor that you couldn't step up and be one of them, in the right place and time. But there are a bunch of factors those of us who spin such tales tend to downplay. Mostly that's because reality, when injected into fiction, is often boring or unbelievable, or both. Truth is never a defense in fiction if the story doesn't draw readers it. "Yeah, but it really happened that way!" doesn't matter if nobody finds it interesting or buys it. This isn't reality, it's fantasy, remember, and by definition, all fiction is fantasy, made-up, designed to evoke certain responses, not the least of which to the writer is that you go out and buy more of his or her books ...
If you are going to be prepared to deal in real deadly violence, you need to train for it. How and where are open to discussion, but watching reruns of Red Dawn or Lethal Weapon, or even reading my books? Not the way to do it.