Watch: On 'CSI' Set as Justin Bieber Plays Troubled Teen

From teen heartthrob to teen terror, ET was on set with Justin Bieber as he took on the role of a bad boy for his acting debut on "CSI."

"I wanted to play a bad character," the musician said of his new role on the hit CBS show. "I'm a nice guy. I'm a good guy. I wanted to kind of play the opposite."

Bieber plays Jason McCann, a troubled teen faced with a terrible decision regarding his only brother -- a decision that leads him into an explosive confrontation with the CSIs. It's the beginning of an emotional story that will wrap up later in the season.

"I'm trying to get into character. I'm trying to feel what Jason is feeling," Bieber told ET. "It's kind of fun. I haven't really done this a lot, but I'm trying to get the hang of it."

The season premiere of "CSI" airs Thursday, Sept. 23 at 9 p.m. ET on CBS.

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