Crypt Zombie

These zombies can be found in dark crypts wandering the halls. They are fairly quiet, and you will often see them before hearing them.

Mechanics (Spoilers)
It's best to turn around if you see them, but if they spot you first, you must run. They are slow, so you can easily outrun them, but take care not to run into others!

The mechanic to avoid aggro'ing them to begin with is to turn off your lights, and crouch past them. You will not aggro them, even if you are right next to them, but be careful: like with any monster, if you accidentally brush against it, it will kill you even if it was never aggro'd. There have been reports that you don't need to crouch to sneak past them as long as you have your lights off, so you can give that a try as well, just be prepared to run just in case!

Trivia

 * On release, the Crypt Zombies used to do a little jig animation when you aggro'd them. This was a bug, and has since been fixed.