SmilingTiger | Points

In this movie I believe that there were a couple of police officers or detectives. The ending of the movie is so very vivid in my head and I even remember a few lines to the song the girl was singing....

I'm not sure if it's a movie or a series. All i know it's that have a guy in the police station bathroom hitting himself in the belly until he turns purple, wearing a sock with a tennis ball inside if...