Robbing or reaping?

This morning I had a little time before I needed to go to work so I decided to walk out and take a peek at the hive and see how the bees were doing. I saw something that I thought was odd, but I'm not sure if I should be concerned.

First some background:
My hive is sitting on a palette which is sitting on cinderblocks which are on the ground.
What I noticed were:

1) Bees sort of walking around on the ground by the hive. I only saw three and they didn't seem to be hurt, they were just kind of walking around.

2) I saw a few yellowjackets zipping around the hive. I watched pretty closely and never saw a yellowjacket enter the hive (or even really come all that close).

3) I think I saw a yellow jacket take off carrying a dead bee that it had found on the ground. I say I think because as I'm sure many of you know, trying to follow an insect in flight with your eyes can be very difficult so I only got a glance.

At first I thought it could be robbing, but when I never saw a yellowjacket entering the hive I thought perhaps that the yellowjackets were just scavening dead bees for food.

I didn't have much time to observe before I needed to head to work so I decided to put on an entrance reducer and I quickly taped pieces of window screen over the vent holes in the boxes.

I posted to the bee board to see if anyone has seen anything like this, and to see if my conclusions sound reasonable.

I am eager to see what people say.