The Biebs delivered a spot-on performance of his summer hit, "Where Are U Now," and his latest single, "What Do You Mean?" -- even flying up into the air at one point -- but then he broke down in tears at the end of the set.
With no explanation at all, Bieber sobbed into his hands while a stunned crowd looked on. Naturally, all eyes were searching for Bieber's ex-girlfriend Selena Gomez, who was attending the show alongside her pal Taylor Swift and the "Bad Blood" squad.
Earlier this month, Bieber opened up about having trust issues after going through hard times in the past.
"Trusting people is hard, especially for me. I've trusted people who I probably shouldn't have trusted before and they've hurt my heart," he said bluntly in an interview with Elvis Duran on his nationally syndicated radio show. "I'm a pretty sensitive guy, so I'll lay it all on the line, and they'll kind of pull it. So now I'm figuring out there's certain people I can't do that with."
For more on that interview, watch the video below.