Screengrab on Twitter/ @NFLonFOX

The San Francisco 49ers-Kansas City Chiefs game got ugly late in the fourth quarter, when tempers flared between 49ers tackle Trent Williams and Chiefs safety Bryan Cook.

The matchup had hardly been friendly up until this point, as the 49ers had previously gotten away with a dirty move on Patrick Mahomes in the third quarter. With the Chiefs up double-digits in the fourth, Williams appeared to be fed up with how the game was going and let out his frustrations on Cook.

Cook appeared to hit Williams on the helmet after a play while Williams was down, leading Williams to stand up and clock Cook in the back of the head. Cook still had his helmet on and was visibly pushed forward by the force of Williams’s punch.

Referees immediately noticed the punch and ejected Williams from the game.

Williams’s blatantly dirty play could see him receive further disciplinary action from the league this coming week. The Chiefs went on to win the Super Bowl rematch, 28–18.