Right off the bat, is that even Foster the People in that picture? I honestly wouldn't be able to tell you. Anyway, I wrote a couple of articles that were somewhat similar to this a while back, and at the time, the comments section was all aflutter with outrage that I'd consider leaving Foster the People's "Pumped Up Kicks" off of a list about songs you didn't realize are secretly depressing.
In my defense, I just assumed everyone already had at least some idea what this song is about. According to the artist who wrote it, a guy named "the lead singer of Foster the People," it's told from the perspective of a troubled teen who's daydreaming about orchestrating a mass shooting. He also added in a later interview that the upbeat melody is intended as a "fuck you song to the hipsters," which makes absolutely no sense to me, but an explanation is an explanation, I suppose.
Hipsters cause school shootings.