He kicked a water bottle away. It seemed to be after the game though so not sure why the ref was that bothered about him doing that when there was so much more going on.
he kicked the bottle towards the crowd, so he was rightly sent off for his actions, according to the rule book
Think it was a second yellow anyway. Difficult to see on the highlights on ESPN but the ref has both cards out. Commentary says 2nd yellow but you only see the ref show the red card despite having the yellow in his other hand. It does seem a strange decision by the ref considering all that was going on.