Even though killing's necessary, it doesn't make it any easier for Carl. It makes him sick. Being emotional is very cool. Being irresponsible isn't. Go tell Bieber!
Everyone says to leave Bieber alone, he's just a kid. Carl's just a kid, but he's fighting for his life every day. Only one would last in the apocalypse, and it isn't the Biebs.
It's not every teen who can responsibly use a firearm, but here Carl is again ready to clear a room of zombies. Would Bieber sing his way out of a jam?