This has some background explanations that help understand the Fed's panicky emergency meeting and slashing of interest rates.

They are worried about a crisis of liquidity in the financial markets, similar to the one that started in 2008 and forced huge measures by central banks to avoid a seize up.

https://www.reuters.com/article/us-health-coronavirus-markets-crisis-ana/the-plumbing-behind-worlds-financial-markets-is-creaking-loudly-idUSKBN2120NJ