[Kou]

or wanders around by himself trying to get more kills/items.

What movie is this?

I meant it more as these are the kind of things if you saw in a movie you'd be thinking "What kind of dumb ass wastes ammo on something you don't need to fight?" But if you want a couple examples, here are 2 I remember.

The dude who was hiding out in the gun store in the Dawn of the Dead. Shooting celebrity zombies and surrounded by hordes of zombies, then ends up nearly starving to death and finally is bitten.

John Leguizamo in Land of the Dead, breaks off from the main group to go get 'supplies' at the liquor store and ends up getting the new kid on the scavenging party killed.