'New uncertainties abound:' What Wall Street's biggest firms are saying about the stock market's sell-off

• Global stocks are selling off sharply this week mainly on investors' concerns about higher US interest rates.
• We've compiled comments from some of Wall Street's top firms on what's driving the sell-off, what investors should be doing with their money now, and what may happen next.

US stocks are in their second major bout of volatility this year, leaving investors, traders, and even non-finance professionals full of questions about what is going on.

The worst of the selling occurred on Wednesday, when the Dow Jones industrial average fell by more than 800 points (or 3%+), its third-largest point drop in a single day. The S&P 500 recovered much of its losses in premarket trading Thursday after a Labor Department report showed that inflation was not as hot as expected in September.

Tech stocks, which have been the biggest beneficiaries of investor dollars during this bull market, have equally experienced the most selling; the Nasdaq Composite has plunged 4.7% this week.

We've compiled commentary from some of Wall Street's biggest firms on what's behind the sell-off, what investors should or should not be doing now, and what may happen next.