The fight happened during the daylight. You're just seeing the dead being carried out afterwards. The picture does look more like a wasp belly to me now.They are pulling drone brood of cells now also.
I'm not so sure. Most of the dead were under the hive (which is on high legs, in an attempt to be skunk-proof) not below the front entrance. And all these dead appeared during the night--I checked the hive in the late afternoon, and then it rained on and off from evening until morning, much of the rain fairly heavy. Would the bees be carting out dead in the rain and not just pushing them off the front entrance? (There were a few dead on the front porch, but the majority were below the hive.) I do have a screened bottom board, but the bees can't get through it. Maybe something was trying to get in from below?
My first thought when I saw all the dead was that they were drones. But my drones are big boys, and these were regular workers, with their guts hanging out. I'm thinking a skunk or raccoon bothered them in the night, but there's no tell-tale perfume to say it was a skunk. I live in a suburban neighborhood of Chicago. We do have possums, raccoons, skunks, and the occasional fox and coyote. I think only the first three could get into my fenced yard.