You're right, it was night time at the church house and everyone was sitting around talking but for some reason Bob had gone outside by the edge of the woods when he got hit in the head.
If you're going to watch it again, after he was hit in the head there was some scrach or scrape on the tree but I don't know what it was.....It may have been something similar to what Carl had found on the side of the church.
Also, earlier when the group was walking, Abraham, Eugene and Rosita were together and Abraham said something to Eugene along the line of "we needed this to happen..." or something like that and Rosita agreed. I played it back several times but it was too mumbly for my ears......
Last but not least, I don't think Bob was bitten in the leg, he was crying about something else....Maybe he was saddened at how the world has turned upside down and it all finally caught up with him.
I figured that Bob got bit in the gross water, but didn’t let on so as not to upset Sasha. When he went outside,they went to a shot of his gun in his back belt. That led me to believe he was going to off himself in the head so he wouldn’t turn.
I wondered if he was turning slowly due to being an alcoholic. Anxious to rewatch the episode.