This has to be a first!

I won't name the airport, but as part of a personal research project into TSA gate searches, I was observing their antics at a boarding gate on the way to catching a flight from a nearby gate. Edited to add: Please note, this was at a boarding gate - not the terminal checkpoint. When I was done collecting data, I did what I always do, which is to take a picture identifying the location and verifying the presence of TSOs, so that I can electronically match the location and date with the data I've collected in my mobile device. Unfortunately, I forgot to disable the flash and one of the TSO's at the jetway door saw me as I turned to leave. He shouted something (couldn't hear) as I walked away rather quickly toward my gate. Since my policy is to ignore anyone who shouts to attract my attention (unless it is advantageous to me to talk with them), I continued walking, but faster. I should point out, I was walking fast because I had spent so much time collecting data that I realized my flight had probably completely boarded.

As I turned a corner, I glanced back and the same TSO was running toward me and still shouting something, but there were too many people in the way. I was almost at my gate anyway. Because of the location of the wall and podium in relation to the jet-way entrance (around the corner), and because all the other passengers had boarded, I was past the GA and into the jet-way in no time. I stood inside the jet-way door, to see if he was coming but I didn't see him walk past the gate (my only viewpoint from the doorway), so he must have either given up and turned around or gone to the gate on the side of the corridor where there was a huge crowd gathered.

SO, my questions are:

1) Who the hell is the TSA to chase me down for taking a picture?
2) the two bozos that always hang away from the gate while gate checks are being conducted were closer to me than the tubby TSO. When he shouted at me, shouldn't they have helped their poor colleague?
3) Had the TSO caught up with me, my response would have been to continue to ignore him verbally except to say something like "if you feel a crime has been committed, please call a LEO". I just want to be sure that there is no such law as "disobeying a TSO", as I would never want to break the law of this fine country, unless I was involved in civil disobedience of some sort.