so wait. You came up on more guys after the string of dudes your just shot in the back(awesome flanking by the way)? or did you mean what would we do with those guys you just shot?
Me personally, I tend to just shoot em once(unless they turn on me) in a nice spot if possible while around the 20ft or longer range. Close enough not to miss, but far enough away to not hurt like crazy or be heard walking up to them.
like you said surrendering someone only rarely works, I'll usually try to give a little kid or new play the option especially if they are buried in a bunker, scared and I know the only way to get them is going to involve a very close range bunker move. Most of them are fine giving up at that point.
in your situation with a pump gun just shoot and get them out. If it is a bunch some could turn and shoot you, so get a jump on reducing the number before giving yourself away with verbals. First indication of enemy is one sitting duck getting shot then the next. My take anyways, subject to new player considerations, and not wanting to get mowed myself after making a good flanking move.
If I have to shoot a newer player at a somewhat close range I try to make sure the are okay after the game and maybe give them a pointer about watching flanks etc.