The Alley

So, at my job, we have an alley. On the side of the store, because we’re at the end of the most boring strip mall in the universe. Sometimes when I’ve been inside the icy refrigerated freezingness that is Plato’s Closet so long that the tip of my nose is cold, like a dog, I’ll go outside and sit in our alley while on my break, eating my dinner. Or lunch. Or 3:00 pizza bagel, or 11:00 Panda Bowl. Or 6:30 chocolate cookie dough shake. Whatever I happen to be breaking to eat at the time, I usually do it in this alley, in order to thaw out. It’s a pretty clean alley, and seems to be friendly and harmless enough when I am in it. There’s nothing out there besides some blown-away leaves and some bags of extra clothes that we donate to a teen shelter.
However.
The cinderblock wall around our alley is shaped like a U, which means that it’s open at one end, the end facing the parking lot, and the other end is closed off. There is no door, no gateway, no empty hole in this closed-off end that would make it possible for any averagely inflexible human being to get out or enter in that way, unless they were to jump over the twelve-foot-high wall. We also are, as aforementioned, the last store in the strip mall. There is nothing to the east of the store but a soccer field that belongs to the elementary school hundreds of feet away. The soccer field is also closed away from our parking lot by a shorter cinderblock wall, topped with about four feet of metal fencing and covered with shrubbery and the like.
However.
While standing at the buy counter that is in the front part of our store, since the weather’s been warm, I and/or my coworkers have witnessed a dozen or so people, on a dozen or so different occurrences, walking nonchalantly out of our closed alley onto the walkway in front of the store. People we’ve never seen before, people we know did not enter the alley the way they came out because we would have seen them, people who haven’t been in to shop, people who usually don’t enter our store as they walk by—we’d probably ask them where they came from if they did come in. We’ve had

-an elderly woman pushing what it looked like was her husband in a wheelchair
-assorted large families consisting of young parents and two or four little kids
-a young guy, about twenty, with a limp and one headphone in, our one regular alley-comer-outer, who talks to himself and fumbles in his pockets, which always makes us nervous that he probably has a bomb
-assorted random little kids. Seriously, like three-year-olds that just come toddling out of the alley by themselves and kind of wander down the sidewalk until we can’t see them anymore
-many other assorteds

Could someone possibly enlighten me on where these individuals are coming from? Is it like Harry Potter where you can just rearrange bricks and crap? That’s our only theory so far.