Back in the late 70s and early 80s, when I got to stay home from school, I remember that around 11am the local PBS channel would air short videos from regional public service stations around the country, or low-budget cartoon shorts with an experimental vibe to them, who knows where they were made or by whom.

One example was of a short fella who sang the same "Ey yey-yey-yey" refrain over and over again, those around him got increasingly annoyed but he wouldn't stop. At the end, a mob slowly converges around the character, encircling him... and he just keeps on cluelessly singing the "Ey yey-yey-yey" refrain.
The mob covers the guy, there's a quick collective roar, then it recedes to show a tombstone. The last shot is of the "Ey yey-yey-yey" echoing as we see the image of the grave, frozen on the screen.

Another one, which I vaguely remember was filmed by a North Carolina public television station, a live action short of a kid that gets bullied at school, at the end the bully or bullies have some sort of accident in the woods, the kid is witness to this, and the shot freezes on the kid looking straight at the camera, with a voiceover along the lines of "What would YOU do in this situation?"... and it ends, right there, not with a resolution but with a cliffhanger and a moral question.

EDIT: grammar for clarity