This film was an interesting one, some really really top notch character work- more so than your average 48hours team, everyone does a great job and is really funny, albeit a touch too old for High Schoolers.
As others have pointed out, the reveal of the crocs at the end felt kind of lackluster, and if you don't mind I'm gonna attempt to dissect what didn't quite work here for me...
I think number 1, we didn't get to see the crocs. It's one thing to describe how ugly and garish they are but it's all nothing without a visual reveal, combined with the guy saying that they were his exact style reinforces this missing element because we don't see him wearing them either.
Number 2, I think we needed to actually see a misdirect at the beginning which leads us to believe the students have witnessed a much more serious crime, perhaps you could have used silhouette to make it seemed like they walked in on the Janitor having hanged himself, or a murder, or theft or whatever, so the whole movie we think they're building up to discovering the dead body or whatever, only for us to return to that scene at the end and discover the thing they walked in on was in fact just someone wearing crocs.
Lastly, we don't see enough people! We don't even see the person wearing the crocs, the characters just stare off into the closet. I'm guessing you guys may have been strapped for actors, so my big improvement note for next year would be to recruit some more extras for standby!
As for your title, I feel like there are a hundred short films called "The Incident" so it doesn't quite work for me.