Admittedly, when I saw the New York Daily News headline, I thought it had to be a totally fabricated gossip story. But...there is video. Or, rather, there was; the copyright holder has had it pulled from YouTube.
Helgenberger was visiting a French outlet of Europe1, to talk about her show (which is adorably known in France as "Les Experts"). Naturally, the subject of recent recurring guest star/international pop superstar Justin Bieber came up, in the context of a discussion about stuntcasting. And though the question was whether Bieber's performance was any good, Helgenberger saw an opening and took it.
After saying that Bieber was "pretty good," considering that he'd "never acted before," Helgenberger doesn't even wait for a follow-up question before going on to describe Bieber's behavior behind the scenes. "I shouldn't be saying this, but he was kind of a brat," she declares. "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 craft service table." (He attacked a CAKE?! I am serious: That is the work of a sociopath.) Bieber's already responded to his nine-million-plus followers on Twitter, tweeting, "[I]t's kinda lame when someone you met briefly and never worked with comments on you. I will continue to wish them luck and be kind." Possibly he typed "kind" when he meant "passive-aggressive."
Bieber had played a slippery young domestic terrorist in a pair of episodes this season; here's an example of his dramatic work.