Federal workers.
They were there just to trim some grass, and pick up a few turtles. Maybe smell the dust in the air. It was hot there also. I am sure they were going to take some pics of the landscape to send back home. It was hot there. After kicking some rocks, they just wanted to go home. It was all so innocent, see?
Maybe even partake in some desert wacky tobaccy. Maybe all that pot being grown on government land has led these BLM cadets to become pot heads. That's the only think I can think of that would transform friendly BLM rangers into blood-thirsty, gun-totting, jack-boot zombies. I just don't know what else could turn them into something like that. /sarc.