TIFU by scaring a boy on a wheelchair

I' been working at my uncle's clothing store for 1½ years now, I'm M18 and do the work my uncle would do when he was in my place, which includes working as a cashier, cleaning the stock room and restocking shelves in the store.

Once a week, monday is what i call "doomsday". Eight hours straight of cleaning the stock room and separating merchandise to 4 different branch stores. Basically a boring day where I have to do a bunch of stuff.

Cleaning the stock is honestly boring as hell so as the years went by I developed my ways to make it fun...

The stock room is on the second floor of the building, and the store is on a pretty busy street, so I developed a fun activity that I call "phantom voice", which involves me scaring people walking on the street by calling them from the stock room window and watching them search for the source. It's usually an inoffensive little prank that I pull on my break on unsuspecting people.

The windows are made out of metal and are built like some kind of "wave" with holes that make it possible to those who are inside to see outside, but not the other way around.

But here comes my fuck up, today I was doing my usual cleaning (couldn't clean yesterday due to a doctor's appointment so it ended up being today) and since I was in a spooky mood due to halloween, my usual phrases like "over here, hello" or whistling, turned into "I see you, I'm watching you" and other scary stuff like that to try and bump up the spook-o-meter.

So there I was, looking out the little window holes when I saw a huge group, probably a family, walking down the street. The thing is, there was a woman who was pushing a boy on a wheelchair, behind the group. I thought of that as a good opportunity to maybe cheer up wheelchair boy's day, planning to open the window and wish them a happy halloween after the prank.

I was dressed up as a vampire, so I made a twist on my original plan to fit my costume, I screamed "WATCH OUT FOR VAMPIRES!" My mistake was not noticing that they were a little too close to the edge of the sidewalk, that got more of a reaction than I expected. The lady turned the wheelchair away from my scream in fear which ended up falling down the sidewalk and making the boy fall face first into what I assume was dog poop.

The family was reasonably angry (and with more than a good reason) trying to find who was the asshole who did that (me). Even my coworkers sent me a text asking if I saw/heard it. That means the family probably asked in the store if it was one of my coworkers that did that.

I went right back to work after that cutting my break short in embarassment and right now I'm writing this on the bathroom, still embarassed at what I did...

TL;DR I scared a woman pushing a boy on a wheelchair through a window, ended up making the lady turn the wheelchair making the boy fall on the street face first into dog poop.