Shot multiple times by an ex with a badge, NYPD detective worked to change the system that she says let her down: "I wanted to be a good cop"

She calls it the "blue wall of silence." Each time Katrina Cooke Brownlee called 911 after her correction officer fiancé beat her, she says the police walked away after seeing his shield. As she shares with "48 Hours" and "CBS Saturday Morning" co-host Michelle Miller,  she took matters into her own hands and joined the NYPD to change the system from within. 

Katrina Brownlee: When I was in Vice as a undercover, I spent approximately … 18 months walking the streets of Queens doing prostitution. … The only difference was that I was working undercover and this was their actual life. But we had a lot of similar stories. … To hear their stories and not able to talk to them about my story and how I survived — it was heartbreaking a lot of the times.