Quote from Nithiel;788353:
Yep. I will blow their heads clear off the second they get bitten or start to freak out and endanger the other survivors.
Pity kill: Subject is being overrun and bitten all over by zombies. They are unlikely to escape and will end up enduring excruciating pain while being devoured.
Don't shoot: Subject was simply bitten in the middle of an attack. Subject may be hurt and somewhat crippled, but he is able to move and fight.
Problem is, if you're in the middle of being attacked by a zombie, and someone is bitten, I WOULD put a little more priority in getting everyone out of immediate danger first.
Once the initial zombie problem is over, then you kill the person who was bitten (or if you're really too soft, ditch them).
If you're using a gun, which I honestly hope you are since you're planning on killing a human, you can't really waste a bullet on a living person when there are zombies. Unlike vidyas, clip sizes aren't ridiculously huge nor can you reload in 1.8 seconds.