In my playthrough as Russell when I was behind the diner, there was a barely alive police officer walker with a screwdriver in its eye. I then had the opportunity to kill him or leave him. since I've played, I've watched two playthroughs on youtube and neither of them had this walker. So what's the deal with that guy? I think he might be the cop who killed the prisoner in the bus, but how did he get a screwdriver in his eye?

Anyone know what I'm talking about?

I'm not 100% sure on this, but I believe his appearance is dependent on the order you play them in and how events that involve that cop in other vignettes

I thought he was the cop from Wyatt's story, actually. Makes more sense that he's the one from the prison bus though.\\

e: maybe dragging or not dragging the cop in Wyatt's story is what determines whether or not he shows up in Russell's?

The cop from Wyatt's story, and the prison bus driver from Vince's story is the same guy. He is also involved in Shel's story as one of the zombie's they have chained up. The zombie with the screwdriver was the one cop from Vince's story that shot the prisoner. You can kill that zombie in either Russell or Bonnie's story. In Bonnie's story when you slide down the hill and get knocked unconscious, you awaken to that zombie. You then have to push the screwdriver through it's head.

This IGN article puts together all of the similarities between all of the stories