While I think I understand your post, I must slightly disagree with you. I, as a LEO, feel it's my business to put my life in harm's way. Period. I do for those that can't, at that moment, do for themselves.
Have you ever read about Beslan? If you haven't, please do sometime. It's eye opening. John Giduck was giving a lecture to Denver PD about what their mission would be in the instance of just such a takeover. He said, paraphrasing, that the mission of the responding officers was to charge the building and die, taking out as many of the terrorists as possible. The objective, you see, is to keep them fighting until SWAT, etc. arrives on the scene and not give them a chance to dig in and fortify like they did at Beslan.
THAT's the gig we signed up for. When your out living on the edge, that's the goddamned job. It ain't about your cool gun and shiny badge and officer courtesy and nice perks and good retirement. Those things are important, but the JOB is to enforce the law for the betterment of society and standing up for those who can't stand up for themselves.
Or it is in my bullsh!t opinion, anyway.
Now, I'm not going to armchair quarterback this officer. It's hard to predict what someone will do under severe adrenal stress. Anyone who says any different is full of crap. But I'd like to think that I, in such a situation, would have done things a little differently.
Maybe I wouldn't, but it's pretty to think so.