I was on board with this theory for a minute, but I changed my mind.

If you watch the video of the exact time this occurred, he definitely grabs at something on the side of his face that’s not visible to the camera with his right hand. For a brief moment, you can see that his hand is bloodless.

However, two people died… so that’s the part that can’t really be staged.

If two people hadn’t died, I’d think he crushed one of those Halloween blood capsule things when he went to duck and cover, but the two deaths lead me to believe otherwise.