I listened to this part on teh way to work this AM.

I firmly believe Michael says Randy!!!
Then, Michael says I may have hit him again
There is something else very interesting...

Michael Shoots Randy in the Arm
Randy Drops Tanya
Michael runs closer to get a better shot
Randy Turns around
Michael sees the face and says Randy!!
Randy says GGRRR or something similar, but it is not one of the generic zombie growls we regularly hear.
It does not start until "randy" is spoken and Michaels narration does not start until the growl is complete
Michael (narrating) refers to the Zombie called Randy as him.

I suspect, there is recognition of both parties. Michael recognizes Randy. Randy recognize Michael.