If you look
here, you can see the game types that are available.
In your game, the game was assassin. In assassin games, you will see only one player with the crosshairs next to their same. Designated by

. Whoever kills their target first wins, no matter who is left on the board.
Hope that answers your question. If you have any more feel free to ask me.
EDIT: Aw, Wicked fastposted me
