I have only done the crib raids so far (3x of them since that's all i had materials to make lockpicks from)
I only killed enough zombies to get past them.
Basically once i jumped in the hole and then got out of the sewer water and up on solid ground I ran as fast as I could down the hallways bypassing as many zombies as I could, and shooting them only when there were too many in front of me to allow me to pass.
Once I got to the end of the sewers and went up the stairs the zombies stopped chasing me.
There was only one container (safe) and it was at the very end of the raid, so maybe its a different one than you did, I'm not sure.
narfi
from what I understand there are re-spawn triggers in certain areas which will revive certain spawns or groups of mobs in the raid, that's why I didn't even try to kill the zombies since there were enough of them to swarm me, I just got out as fast as I could.