This is what triggered the officer, please watch the entire video before commenting.
"Go back to Mexico!" the teen yells.
"I ain't from Mexico, you stupid [expletive]!" Officer Rosario fires back.
Attorney Dan Fultz says Officer Rosario had reached his limit with a 19-year-old standing at a potential crime scene.
The officer comes back to the same home and the teen doesn't disrespect him and says its all good
Officer gets punished
http://abc7chicago.com/news/body-cam-captures-officer-punching-teen-/1813250/