Shares of Berkshire Hathaway ( BRK.A 0.06%) ( BRK.B 0.18%) are falling on Monday. The company's stock lost 4.3% as of 11:45 a.m. ET today and as much as 6.8% earlier in the day. The leg down comes as the S&P 500 lost 0.5% and the Nasdaq Composite lost 0.7% on the day.

Berkshire Hathaway (BRK-A, BRK-B) stock fell as much as 5% on Monday before paring losses as the conglomerate's board said it had unanimously approved longtime CEO Warren Buffett's appointment of vice chair Greg Abel as his successor,

"You're losing one of the most esteemed investors one could argue of all time," a source said of investors' reaction to Buffett's plan to step down.