Yeah, Blake was a cop. He killed those men (out of self-defense) before fully becoming 'Robin', so to speak.
As far as Batman killing people in this series, people greatly overreact about this whole thing. Batman (in Nolan's series) never killed anyone directly. By that, I mean with the intention to murder another person. Most deaths which were cause by Batman could be considered "collateral damage" during times of great distress..except for Ra's, which Nolan even admitted he was on the fence about. In TDKR, the death of the truck driver was due to Batman frantically attempting to avert a nuclear disaster. He was trying to get the truck to change its course by shooting his cannons in the truck's path. If anything, it's the truck driver's fault for not changing course and driving straight onwards (under Talia's orders).
Dent died as Batman made a last-second dive to save a young boy from a madman. Now, if Dent was standing there by himself and Batman shoulder-bumped him off the ledge, that would be murder. Instead, Batman did exactly the right thing by essentially tackling Dent and grabbing the boy.
My point is that Batman hasn't killed anyone in cold blood. His rule is no guns, no killing...and he has stuck by that in this series. He hasn't aimed a weapon at someone with the mindset of "I'm going to kill this person" (as Batman did in B'89 when aiming his Batwing missiles directly at the Joker). But there are casualties in every war and Batman does fight a war on crime. His casualties are clearly unintention and sometimes unavoidable.
Note -- Any deaths he caused when escaping from the LOS headquarters in BB should be considered out of self-defense. He wasn't going to murder the man they set before him. Upon realizing that he was living among a radical group of 'murdering psychopaths', he reacted quickly and did he was had to do to orchestrate his own escape to safety. Shouldn't be considered murder by any means.