This happened to myself and a close friend (both 23 y.o. males) just last month.
We decided to go on a two night backpacking/camping trip in the Adirondack mountains of New York. We are both very comfortable with nature, and spend a lot of time camping, hunting, fishing, etc.
We hiked about 5 miles into a small lake and set up camp on a small beach. This was not a heavily trafficked area, and we did not expect to run into anyone. Our first night there as we were sitting around the fire, we saw a flashlight moving on the other side of the lake around 10:30. This was fairly unusual, however we did not think too much of it.
But, as time went on, this flashlight kept moving around the lake getting closer to our campsite. We kept discussing who could possibly be wandering around the woods in the middle of the night, and we did not particularly want an unwelcomed guest.
Once it was clear that the person (or people) were heading for our campsite, we moved off into the woods nearby to see who wandered up. I took a small axe with me, and he had a .22 rifle. Now we weren't expecting trouble, and we certainly didn't want to make any, but we figured we might as well cover our bases.
Now, the moment of truth, the flashlight comes near the light of our fire and it is one man. He has a beard and is probably in his mid 40s. The scary part was he was carrying what turned out to be a pump action shotgun. He walked around the campsite a few times, and then proceeded to enter our tent. After rummaging around for a minute or so, he came out and started yelling "I know you're out there, why don't you come and say hello?".
My friend and I remained motionless under a hemlock tree about 50 yards away. That is when the man proceeded to fire his shotgun into the woods (not too far from where we were). He also swung his flashlight around several times. After what felt like hours, he grabbed my friends backpack and a few articles of clothing we had drying off near the fire and threw them in to burn.
My friend, who had trained the .22 at the man, asked me if he should shoot. I told him absolutely not, unless he spots us and starts to point the gun in our direction. Thankfully the man moved off from where he had come after a little while. We waited until his flashlight was on the other side of the lake, ran out, grabbed everything we could fit in my pack and took off (it was now around 2 or 3 A.M.).
We RAN out the trail with flashlights, and made it back to my car as the sun was coming up. We immediately went to the police department and reported it, where we also spoke with some forest rangers. That was it, I haven't heard anything back from the police. It wasn't mysterious, however it creeped the hell out of both of us.
TL:DR- Camping, man with gun in the night, almost had a firefight.
Edit: Holy crap baskets this blew up. Trying to respond to as many people as I can. If you want me to read what you say reply to this comment.
Edit 2: So this is what it's like to have a top comment on a front page post. I'm trying really hard to respond to people. I've been typing nonstop for 3 hours.