Okay sense guns have no conciousness they can't be evil but I'm assuming you mean the use of guns is evil.
In that case. If a man breaks into my home with every intention of harming me and my family and I shoot him dead in self defense, is that evil?
Did he plan to kill you? Could you have just shot him in the leg and left him alive? Did you do something to provoke him, such as breaking into his home and harming his family? Are you satan?
Answer these questions then i can decide if that would be evil.
In all cases where my family is in danger I assume the worst. I wouldn't know whether he had planned to kill unless he blantantly stated it. Either way I'd probably kill him. Why? In Louisiana (aka Lousyana) you can break into someone's home, be shot in the leg or you can just slip in some water on their kitchen floor and you have the right to sue them. If that's not the dumbest law I've ever heard. Regardless, in my eyes if you mean to harm my family, death or not, I'd kill to protect them.
Let's also assume that I've never met this man before in my life. He's simply breaking in to a random home for personal gains whether it be theft, pleasure from torturing and/or killing us, or just for sport.
And lastly, LOL, I don't really believe in Satan and do not recall any converstions with celestial beings so I'd have to say no.