U.S. stocks sold off in the final hour of trading as a decline in crude oil prices picked up speed during Monday afternoon. West Texas Intermediate fell nearly 6 percent, though managed to hold above $30 a barrel. SunEdison (SUNE) climbed on reports David Einhorn's Greenlight Capital will appoint a director to the board. The solar company has suffered a stock price slump and a number of C-suite departures recently. An announcement could be made this week. Sprint (S) is allegedly planning thousands of job cuts as part of a plan to reduce costs by $2.5 billion. The telecom could eliminate 2,500 positions, equivalent to 7 percent of its workforce. D.R. Horton (DHI) fell after it delivered disappointing sales growth to end 2015. TheStreet's Keris Lahiff reports from Wall Street.