When he put them in the barn, they were people that he knew (or at least Hershel knew) and if he was staying with Hershel, then it's Hershel's say and he'd want to do right by him, he knows he's a nice guy. When he was shooting the walkers when they went for the medical supplies, he was killing for survival, to do right by Carl and get the supplies back. Also, those walkers were a real threat, so many of them, trying to kill him, he wouldn't show any mercy.

How many were there in the barn? A dozen, give or take? To bring those back to the barn they weren't a threat, they had those collar things and didn't really have to worry, there were many more trying to kill him at once when he went with Shane, the scenarios were completely different.

Just my take on it.

 

^Agreed (though I didn't think about it at the time lol).

I think it was likely that Otis was following Hershel's rules while in his care. But then again, we all know that killing someone is wrong; but its a different story when someone is barrelling down on you with the intent to kill and you happen to have a weapon in hand that could save your life if you used it...(if that makes sense).

 

I understand.

It may have also been putting SOME of the walkers in the barn to please an old man with a warped sense of what is going on, and killing the rest.

There was a look that Hershel an Otis shared before Otis and Shane went to the high school.....hmmm..

 

He killed those walkers for survival and to take those things to Carl as fast as possible, but unfortunately we all know how he ended. If someone else was in his position that person would have done the same thing.