How do you react to this?
I find myself saying this a lot, but am torn between a) not wanting to make a big deal of it so he knows he gets a reaction, and b) wanting to stop him saying things like "I'm going to shoot you / kill you" etc, even though I know he doesn't mean it/ understand what it means, he's just copying what he's heard other kids saying.
So far I have just calmly said to him that words like "kill" and "shoot" etc are not nice because it means hurting someone and making them sad.