This shows the importance of situational awareness. Sounds like this happened so fast, even if she was carrying she probably wouldn’t have had time to draw and take out three targets. You have to be aware of what’s in front of you and any blind corners - and change your path to avoid bad spots. If you do see someone suspicious to you (and you are carrying) always try to keep something between you and him/them - a car, a trash can or even a telephone pole. Something they would have to go around to get to you, which should give you just enough time to draw and confront the threat.
It happened in D.C., it's next to impossible to get a CCW in D.C. for anyone other than the most well connected, and the well connected generally have armed security.
Blind corners work both ways...the criminals can't see you coming either. And bad spots can be anywhere...criminals are portable.