S&P 500 Ends below 4,000 for 1st Time since March 2021; Growth Shares Lead Decline
* Nasdaq drops more than 4%* Twitter falls as short-seller Hindenburg flags risk to Musk deal* Indexes: Dow down 2%, S&P 500 down 3.2%, Nasdaq down 4.3%NEW YORK, May 9 (Reuters) - The S&P 500 ended be