Usually it's just on the far side, but I see its poop in front of the pen, too.
When it's just sitting there or moving slowly, they stand there with stretched-tall necks and fanned tails doing a typical repetitive warning squawk, crowding on whatever side of the pen is closest. When it runs, well, you saw the video.
Honestly this probably is related to a problem that's been going on for a lot longer. I thought it was getting better but maybe it's just shifted.
Here goes:
-Months ago, my mom (who is scared of chickens) had a container of kitchen scraps to feed them. She opened the door of the pen just enough to toss the stuff out of the container (probably one of those blue plastic things mushrooms come in at the store) and that freaked out the chickens. They panicked and ran to the other end of the pen and squawked for a while. (And ate the treats immediately after they calmed down.)
-I learned soon after that ANYONE who throws/drops food into the pen from the doorway can cause a flock-wide panic. If you close the door behind you and throw from there, they freak out. The closer to the door you were standing, the more upset they'd get.
-My mom hasn't done it since, but the flock has only gotten more sensitive over time. If I was too sudden throwing layer pellets on the ground with the food pail, they would panic even though they know it's the food bucket and they're hungry. This was no matter where I was standing.
-It has gotten to the point that they might all be eating as peacefully as chickens can, a hen shakes off for one reason or another, and every chicken around her is scared. (The hen in question also runs since everyone else did.) I've seen it happen more than once.
-I think it's gotten better but I try very hard not make sudden movements inside (or in view of) the pen. It was happening one to three times a day, whether or not anyone was outside, but at this point I might not notice.
So, yeah, I guess the rabbit-phobia is probably related to that, which is the weirder problem. It's like they've developed a mass anxiety disorder or get mass hysteria.