The Woman in the Pink Dress

Your new neighbor is a young man living alone. One day, returning home after a late-night snack, you see a woman with long hair, wearing a pink dress and heavy makeup, enter your neighbor's apartment. Late at night, you hear arguing and things being thrown, which is particularly jarring in the quiet hallway. The next day, you see a shredded pink dress and a bunch of long hair in the garbage bag outside your neighbor's door. When you ask your neighbor about it, he stammers and refuses to explain... Should you call the police? What happened?