So what is this Kirkpatrick event from '09 that McCain can't stop talking about?

[Attorney General & PPT Dwarven Dragon]

In a bunch of McCain's TV ads, he shows Kirkpatrick walking out of a town hall event in August 2009 with crowds still there. The ads claim that she stormed out after being grilled on her support for ObamaCare. McCain's really running with this:

https://www.youtube.com/watch?v=L1J89Pzgzbg
https://www.youtube.com/watch?v=qPTcbU3nkVs
https://www.youtube.com/watch?v=YEbzyTTFJdA
https://www.youtube.com/watch?v=y6ef7bZRZoI
https://www.youtube.com/watch?v=voQCyHt3EDg

So what happened here anyway? I saw something about a security risk at the event at one point, but don't know how valid that is. While my endorsement probably stays with Kirkpatrick regardless, I'd still like to know a non-partisan version of what happened.

[Sprouts Farmers Market ✘]

You probably don't want to un-endorse her just to avoid the embarrassment of having to un-endorse.

[Attorney General & PPT Dwarven Dragon]

You probably don't want to un-endorse her just to avoid the embarrassment of having to un-endorse.

I feel no pressure to do it as the pattern of my endorsements already endorses a republican senate. Plus this doesn't change the fact that McCain isn't a maverick anymore. (though some of my endorsements are clearly not going to happen, for instance I've endorsed Long in NY and Milne in VT, but whatever.)