they guy with the ear wire does look lighter skinned than the one in the pix that was taken after the bomb went off (one with 2 of them with phones to their ears) - they may have had a tip that there was a bomb threat and had undercover LE walking around and they may be LE.
The Alabama or Mobile Cross Country Coach said someone was making announcements there was a drill. Either he or someone else said there were bomb-sniffing dogs which they had never seen before at such an event.