UPDATE 2-> Bottom of this post

Basically, a zombie dressed as a scientist (lab coat and all) will run up to you (assuming you don't shoot him) and literally steal your load out; He yells "MINE!!" and you character does the little hand motion where he's like "nooo don't take my weapon away ". He takes away your weapons, and any sort of drinks (Quick revive, juggernog, ect.) and leaves you with a colt. You will then have to chase him throughout the map, and try to shoot him, and trust me it's not as easy as it sounds. If you get too close to this dude, he starts putting portals down to random places in the map which ANYONE can access; he's a wily little fella.

Some other points to include are:

*If you kill him before he steals your load out, then you get an achievement and automatically end the round.
*There are no other zombies present when you try to chase after this dude.
*He dissapears after around 5 mins (don't quote me on that)
*If you manage to kill him, you get a max ammo (Wah wah wah.........)
source: cod forums


UPDATE:
LOOK @ 7.18

screenshot in case video gets deleted
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UPDATE 2:
Yes,you can kill the thief, EXCEPT THAT IT TAKES A LOT OF FIREPOWER TO KILL HIM
the guy had to put mods(infinite ammo) to kill the thief lol ,
And,Yes it does take alot ,lot of bullets
see below:
the 'fun'' starts @ 0:40
it's FINALLY dead @ 1:14
it gives u max ammo (hopefully,because without mods,u prolly wasted a lot of ammo)
and also give sale ,in case u wanna buy stuff...

I won't take screenshot for this video because it's mostly something to watch
beside there are some backups below in case it gets blocked

BACKUP:

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