Question: Dick Costolo was the CEO of which company before the co-founder took over in 2015?
Sentence (from "Dick Costolo"): On June 11, 2015, it was announced that Costolo would step down as CEO on July 1, 2015 and would be replaced by Twitter co-founder and chairman Jack Dorsey on an interim basis until the Board of Directors could find a replacement.
Relevant evidence: Yes