He was described as "a little brat" by one of the cast members on CSI when he was a guest star. He shoved his hands into a cake, and locked one of the producers in a closet. It's most likely the reason they killed off his character. Talentless or not, he's a little shit. 

EDIT: [Source](http://www.newser.com/story/118116/marg-helgenberger-csi-star-says-justin-bieber-is-a-brat.html)