This act of police brutality has to be one of the most shocking we've seen in a long time for the sole reason that the police officer in question reacted so irrationally without having any knowledge of what actually happened.  It was also horrible because the officer actually felt he had the right to punch a small woman in the face while she wasn't looking at him, all because some water got thrown on his back during a parade.  

At the Puerto Rican Day Parade in Philadelphia, a Philadelphia police captain sucker punched a woman who he believed had thrown water on him.  According Gisela Valentin, the woman who recorded the video, the victim of this police brutality was spraying silly string into the crowd; however, that was not what made the police captain sucker punch her while her back was turned.  While she was standing behind the crowd of police officers, you can clearly see a man step forward and throw water into the air which splashed down on the woman and the police officers.  She quickly turned around to see who had thrown it and began walking toward the sidewalk, at which point the police captain angrily approached her from behind.  

The woman turned to him unsure of why he was creeping on her in such an aggressive way, and when she turned back to the sidewalk, he cold-clocked her right in the mouth which sent her dropping like a brick to the ground.  He then forcefully pulled her hands behind her back and put handcuffs on her.  When he drags her to her feet and had police officers take her to a nearby police car, you can clearly see that her mouth was bloodied from the punch.

There's no word if this officer face some form of punishment for his actions.