Also, unless he was highly stressed (like sweating, breathing heavily/hyperventilating, having tremors or shaky hands, and had a shaky or raspy voice when you told him you're ending the relationship) I doubt he had a breakdown.

It's more likely he is lying and causing pain to you. Did he had butterflies in stomach? Did you notice something odd? Did he talk about psychological evaluation he ever had (if he did)? Unless he sought professional help for his delusions, I doubt it is true.
Edit : My mistake, I didn't notice you live in New York. The Police Department must be busy.