That's their mistake, then. They should boot the character, all in good fun at the table but deadly serious in character. Or - and I've seen this done - next time he starts a fight expecting backup, hang him out to dry and don't give him any.Group think squashing creativity?
The characters whole thing was that he fired upon anything he saw before the other characters got a chance to interact with it.
He was squashing everyone else's creativity by not allowing them to play their characters.
In the narrative of the game those characters would all boot him from the party because he will get them killed. They only don't do it because it is a game so he must be included.
Thing is, it's usually the players of individualist and do-your-own-thing characters that are labelled as problem players, and I'll fight that all day long.Reigning in a problem player is not squashing creativity.
I want players who think for themselves, and who have characters that can think for themselves, and who are willing to have their characters act on those thoughts with or without regard for what the other characters might think; and if that ends up as a DM-side exercise in cat-herding I'll take that every time over a group who all think alike or who just passively follow the lead of one dominant player.
Your shoot-first guy is just the sort of character that makes the game fun and, all too often, is what gets the game moving. More, please.