Casing Out a Coffee Shop to Plant a Bomb?

Here in West Palm we are still, after about a week, under a boil water advisory.
So, today I was sent out to photograph the closed Starbucks in various
locations in the city. On Clematis Street downtown, I was crouching
below the large "We are Closed" sign in an effort to get rid of glare
when a cop on a bike approached, "Can I ask what the purpose for your
taking pictures is?"
"The Palm Beach Post" I tell him, and he is satisfied with that
answer. In my head (in this what if scenario), I ask him "What's the
purpose of your nosiness and stupidity?"

I'm wondering to myself what possible questionable thing could I have
been doing with my camera that would warrant asking. I mean, even if I
was shooting into the shop, I'm still on public property.