From the Federal Reserve: Federal Reserve announces extensive new measures to support the economy. There are several actions in the announcement including:
The Federal Open Market Committee (FOMC) will purchase Treasury securities and agency mortgage-backed securities in the amounts needed to support smooth market functioning and effective transmission of monetary policy to broader financial conditions and the economy.
This is especially important for the mortgage market. The Fed will buy whatever it takes to stabilize MBS.
There is much more in the announcement (including supporting large and small businesses). This is a “whatever it takes” moment for the Fed.