Selena Gomez -- Dissolves into Tears Over Christina Grimmie Murder

Selena Gomez broke down in tears Saturday night as she dedicated a song to former "Voice" contestant Christina Grimmie, who was gunned down Friday night after an Orlando concert.

It was very personal ... Selena's stepdad signed Christina when she was just 14 to manage her singing career. Selena was Christina's mentor.

Gomez dedicated "Nobody" to Christina.

As we reported, Christina was gunned down during a meet-and-greet by an obsessed fan.