Kacouris said the marketplace was “shocked” when “the truth” began to emerge on Wednesday from the Menlo Park, California-based company. He said the 19 percent plunge in Facebook shares the next day stemmed from federal securities law violations by the defendants.

The lawsuit seeks class-action status and unspecified damages. A Facebook spokeswoman declined to comment.

Shareholders often sue companies in the United States after unexpected stock price declines, especially if the loss of wealth is large. 

Facebook has faced dozens of lawsuits over its handling of user data in a scandal also concerning the U.K. firm Cambridge Analytica. Many have been consolidated in the federal court in San Francisco.

Thursday’s plunge also hit Zuckerberg’s bottom line.

Zuckerberg had been tied with Warren Buffett as the world’s fourth-richest person, but the Berkshire Hathaway Inc (BRKa.N) chairman’s current $83 billion fortune tops Zuckerberg’s $66 billion, Forbes magazine said.

Buffett now ranks third among the world’s billionaires, while Zuckerberg is sixth.

Facebook shares fell another 0.8 percent on Friday, closing at $174.89 on the Nasdaq.

The case is Kacouris v Facebook Inc et al, U.S. District Court, Southern District of New York, No. 18-06765.