The initial attention was because it was blocking, or at least interfering with where buses needed to turn. It also was running and had it's flashers going. I hope something like that would draw my attention. The guy I saw interviewed, the street vendor, was a very well spoken, and "clean cut", black guy. Not at all the image that you might have of Times Square street vendor. I was really surprised. He is also a Vietnam veteran, and might just have a bit higher than usual sense of "something not right", developed the hard way.
I saw Duane Jackson on Fox this morning. I tend to agree with your assessment of his character. I’m still not clear about the other vendor, Lance Horton, who has also been credited with alerting.