ViacomCBS Inc. (Nasdaq: VIAC) shares plunged 27% or $18,12 on Friday in the biggest one day sell-off since 2008. The sales approached $30 billion in value, some of the people said, and fueled a 27% plunge Friday in shares of ViacomCBS -- an unusually large decline in a widely held, large-capitalization stock on a day with no significant company-specific news. According to Bloomberg, Asian hedge fund manager Bill Hwang was behind those transactions.