I actually hadn't seen the video before, I just knew and liked the song, so mine was an unintentional mistake. This teacher's mistake was intentional:
A Bronx middle-school teacher rattled her students — including one who was near tears — by showing an ISIS video of a terrorist beheading a journalist, documents show.
South Bronx Academy for Applied Media veteran Alexiss Nazario faced termination, but was let off with a $300 fine last summer after acknowledging she made a mistake by not previewing the clip or getting the principal’s permission...
The students testified that the video blacked out the actual beheading but showed its gruesome aftermath: the man’s severed head placed on top of his own chest.