"If the helicopter was taking off then he's legal. Also since you
described the area as mostly vacant fields, I believe that would
qualify as a sparsely populated area."

Just the Wal-Mart parking lot full of cars (a few hundred vehicles just
then).

"Also since it's a helicopter they are allowed to operate less than the
minimums unless it's hazardous to people and property on the ground
(other than percieved altitude, was
the helicopter doing anything seemingly dangerous?)."

Other than apparently flying straight for the front windows of
Wal-Mart, no.

"On a side note concerning Walmart, you can't be without your camera
for more than an hour or two while you shop?"

Bite your tongue, man! My camera is my soul!

Also, my camera cost me $580. I'm not keen on leaving it in my vehicle
in a public parking lot.