Cam, welcome to the board. IMHO you did goof by firing into the air. I understand your adrenaline was pumping. No one was hurt, don't let it happen again. Next time could end up with someone hurt or dead.
As for the "other guys" they could well have been Forest Service employees. I was a seasonal worker on Helena NF in Townsend, MT and the only uniforms we ever wore were our yellow and green nomex when we were on a fire. The rest of the time it was whatever was comfortable. Trails are optional. We took many shortcuts cross country at the end of a shift. As for the guys appearing nervous - well I would be too. You've got a group of folks in the dark, yelling and shooting at who knows what. Not a scenario to walk/ride into without keeping your guard up at least a little.

That's my $0.02
Ed