We need to let the authorities know that we are good for them. Those of us who visit airports on a regular basis often know before the airport police when something is out of place. At my home airports, TUS/PHX, the airport police are used to seeing me around. Especially TUS. They know me here and, even before this tragedy, often stopped and asked me if I've seen anything out of place.
Might not be a bad idea, when visiting a strange airport, to announce yourself and be VERY obvious what you are doing. At MZJ when we see someone who is very obvious trying to find a good shot from the perimeter, we don't worry much We see them but don't worry much. It's those people that try to hide that we worry about.
Go about your spotting. Just realize that there will be much nervousness for a while.
Regards to all and prayers for those many who lost loved ones.
The day you stop learning is the day you should die.