In my campaign we see a civilian we murder him so I was wondering in your campaign what do you do

It depends on where the civilian is seen. We'd probably talk to them or ignore them.

Most likely ignore them, but sometimes our psychopathic druid who enjoys filling the lungs of a creature with water might do so.

In Our main campaign, the players are an emissary's of the people, so we tend not to kill civilians. We usually attempt to convert citizens to the worship of our pet dragon, who is currently a demi-god thanks to this, and a few thousand kobolds.

Your players are probably what's known as murder hobo's.

Depends on which campaign you're talking about. I have, like, 13.

For most campaigns, we usually talk to them (if they're unimportant), invite them into our party (if they're really unimportant) or ignore them (if they're really important), unless they try to kill us, in which case we kill them.

I almost always talk to folks that we encounter in the wilderness. I figure they probably know something helpful about the area. But, I enjoy playing Bards, so you would expect me to do that, even when I'm not playing a Bard ATM.

I couldn't call it a campaign, but when I get to play, I usually talk to civilians, and I usually initiate the conversation.  When I DM, a couple players have already been imprisoned for murdering every NPC they saw.  I mean, wtf?  I have to come up with a backstory for every one of them!  That's a lot of work!

Quote from PugofUtterDestruction >>

Depends on which campaign you're talking about. I have, like, 13.

For most campaigns, we usually talk to them (if they're unimportant), invite them into our party (if they're really unimportant) or ignore them (if they're really important), unless they try to kill us, in which case we kill them.

This defines The Oxventurer's Guild.

As for what I would do? I wouldn't go around murdering every civilian. Too much of a grind and waste of time. I'm there to adventure, not to keep rolling dice for no reason. If the DM is all like, "You attack the civilian and the person dies," with no dice involved, what's the point? I might as well just play some bullet-hell video game.

If that's someone's bag, bully for that person, but I'll sure never understand it and will probably just go to another table out of sheer boredom.

If you want to just go around murdering random bystanders just play GTA. I honestly think that players who react to everything and anyone with "kill immediately" are at the very least uncreative and dull, and might possibly be in serious need of real world therapy for any of a number of reasons.

Try and stop my friend the necromancer from killing them.

Either talk to them or ignore them.

as a DM, if I were running a game for murderhobos (IE, see a civilian, kill a civilian) they had better be prepared to encounter that level 20 retired vengeance paladin who was walking down the street to buy apples for the orphans in his orphanage. Or that one guard who's actually a level 10 fighter, and has been denied advancement by a corrupt chief. Or to find out that the bird on the civilians shoulder was a druid. And so on.

Try to murder the world, and make the world a place where everyone dies? Guess who's dying?