It's my bad, mate, I'm the one what was nonspecifical about it.

In essence: He sees a symbolic representation of your personality. For Murphy, he saw an avenging angel, because that's the metaphor for the role she has in life- a police officer who works genuinely, bravely, and selflessly to protect the people of Chicago from the darkness in the world, and remains uncorrupted by it. She's an angelic figure, in other words.

And the gun, in an extension of the analogy, would be the sword she uses to smite only the unjust. It's all rather allegorical.