First, my point here isn't to defend the Capitol Police and Secret Service. It's awful that a woman, apparently in the throes of severe mental illness, was shot to death. I want to explain why their actions don't surprise me at all and seem justified based on the facts the police knew in real time.
Obviously our information is still very fragmentary. So let me start by saying that I'm operating on the assumption that the essential story we've learned so far is accurate: that Carey attempted to break through the White House security perimeter with her car, then fled and proceeded to led Secret Service on a high speed chase toward the Capitol building where she appears to have refused to surrender when cornered in her car with at least four police officers holding guns on her at point blank range demanding she get out of the car (see this video), flipped the car into reverse and continued the attempted get away until eventually trying to flee her car and being shot to death by Capitol Police. If that story changes, obviously my take could change as well.
Start with the the assumption, which I think is almost certainly right, that the Secret Service's main fear for the President's security within Washington and the White House complex is a car bomb. That's why the security perimeter has become so large. That's why Pennsylvania Avenue is now blocked off in front of the White House - something that's had the unintended effect of creating a very pleasant pedestrian promenade in front of the White House. Remember, the closure of Pennsylvania Avenue in front of the White House happened in the immediate aftermath of the Oklahoma City bombing in 1995.
In any case, if you try to ram through the White House security barrier with a car, I think there's little question the Secret Service immediately goes into attempted assassination, car bomb mode and proceeds accordingly. If you flee toward the US Capitol and resist arrest, I think you've probably signed your death warrant unless you very clearly surrender.
This is all sounds kind of harsh and perhaps of crazy from the outside. And it totally may be. But I don't think it's surprising when you understand or have experienced the intense security posture that surrounds the main government installations in DC - the White House, the Capitol Building, the congressional office buildings, etc. That chase from the White House wasn't a traditional chase and apprehension, probably more like a hunt, with threat elimination as its primary goal.
I was talking to a friend yesterday afternoon. And we were speculating on whether Carey could have been confused by where she was when she tried to force her way onto the White House grounds and simply panicked when she saw she was being chased. Perhaps she didn't get a chance to surrender. Some sort of panic tied to emotion disturbance seems possible here. But in the broader sense, this scenario doesn't seem very plausible.
What struck out to me is the scene in this video in which Carey is right next to the Capitol, is surrounded by 4 or 5 cops with guns drawn basically only feet from her car telling her to exit the car. Instead she rips the car into reverse and bolts, showing along the way some pretty honed evasive driving tactics, which I suspect further heightened the threat level in the cops' minds.
This is a tragedy. Carey was apparently unarmed and presented no threat other than the ability to ram people with her car - which lets remember, can be a pretty serious and lethal threat at least to limited numbers of people. The chance of extreme mental disturbance seems high and - horrible to contemplate - her 18 month old daughter was with her in the car. But given what was known and her behavior, it makes perfect sense to me that the Capitol Police and whatever other federal authorities were in the mix were focusing on threat elimination as their primary goal rather than apprehension. Even the attempts to get her to surrender were rebuffed.
Given what security personnel around these buildings are taught to expect and how they're trained to respond, how this played out should not surprise anyone.