Justin Bieber is a brat!

Justin Bieber “was kind of a brat” when he appeared on CSI: Crime Scene Investigation.

The 17-year-old superstar made a guest appearance in the drama TV series playing troubled teen Jason McCann, who was shot dead, in the series finale, and according to actress Marg Helgenberger some of his behavior was unacceptable.

Marg who plays CSI investigator Catherine Willows in the show claims he locked a producer in a cupboard and ruined a cake.

“I shouldn’t be saying this but he was kind of a brat,” Marg said.

“He was very nice to me. But he locked one of the producers in a closet and he put his fist through a cake that was on the cast’s table.”

Despite Justin’s misbehavior on set, Marg, 52, insists he is a competent actor especially for someone with no prior experience.

“Justin Bieber wasn’t bad,” she said. “He’d never acted before … He’s better than you’d think.”

At the time of his appearance the annoying Baby hitmaker said he enjoyed getting into the role, especially when his character came to a dramatic when he was gunned down in a stand-off with police.

“It was really cool because I actually I get shot, like several times,” he said.

“I fall down and there’s fake blood and everything. It’s crazy how the whole process is.”