First US Plane fired on?

Hi all,
I live near a fort called "Fort Brown" in Brownsville, Texas and there is an
historical marker that reads, "'First Army US Warplane', on this spot was made
the first flight of US Army plane to be fired on in armed hostilities on April
20, 1915." Then it goes on about how the planes were a group of signal corps
officers who were out scouting the area near the fort due to heightened Mexican
hostilities in the vicinity. The planes were hit by machine gun fire, etc. I
also read elsewhere that (not on the marker, but from an autobiography of a
pilot) that the first aviation dogfight also ocurred nearby when two pilots
with pistols duked it out in the skies with their Curtiss Pusher aircraft.

Does anyone have anymore info?