Because I got a multi kill in three seconds and lag shot (when they are killed but the game is slow and so they die when moving away) someone.
I had a similar thing happen the other day.
Same map, elim pro. It was me vs the rest of the other team (1v4, I think). I was waiting on the right side of the entrance to the map room, and 2 guys came in and ran towards the opposite side of where I was, so I shot them in the back for a double kill. Then, another guy came in and stopped, so I killed him for a multi kill. Then, the last guy ran in and did the same thing as the first two guys, and turned around to shoot when I started firing at his back. He was too slow, however, and I killed for an ultra. That was reason enough to kick me.