The stock market experienced significant fluctuations with the Nasdaq hitting a record high initially but later struggling as bond yields spiked. The Dow fell over 300 points and then tumbled further due to rising Treasury yields, impacting megacap stocks. Concerns about the timing of Federal Reserve's interest rate cuts led to futures falling as bond yields rose, pressuring stocks. Indexes slid as bond yields continued to rise, with the Dow down over 400 points and jittery investors on edge.