Twitter (TWTR) surged after the bell on news CEO Dick Costolo will step down from his role effective July 1. Chairman Jack Dorsey will assume the position in the interim until a replacement has been found. Yahoo! (YHOO) took a dive after research firm Capstone said potential changes to tax laws by the IRS appeared 'carefully choreographed' to 'send a message' to the company. Any change to the laws could affect Yahoo’s plans for a tax-free spinoff of its stake in Alibaba (BABA). Hess Corp (HES) jumped after it said it would sell a 50% stake in its Bakken midstream assets to Global Infrastructure Partners for just under $2.7 billion. The majority of S&P 500 sectors climbed, boosted by rebound in retail sales which showed earlier economic weakness was merely transitory. Transocean (RIG) and Diamond Offshore Drilling (DO) fell alongside oil prices.