504 Running Across Rooftops

One night I was in the wrong place at the wrong time. I walked through streets that were quiet until I got surrounded by big dark figures with weapons. Just when everything seemed dark I found myself high above the streets, being carried across rooftops.

"Come with me if you want to live" said a serious feminine voice. I looked up at her and her face was concealed. She looked slight, but must've been incredibly strong to carry me. I looked behind us and there were the same guys chasing us. 

She sat me somewhere cramped and dark. "Stay in here a while" she said. I could see nothing but heard the sounds of loads of guys being beaten up savagely.

"Safe to come out now" she said. I climbed out and saw the corpses of my attackers strewn around the place.

She then picked me up again and leaped off the roof, sailing across the street to the rooftops on the other side. Then she lay me down on my apartment building roof. "Look after yourself, cutie" she said, before giving me a kiss and disappearing into the night. Who was this girl?