The CEO of Fiat Chrysler has stepped down after a company statement says he suffered serious complications following a surgery. Sergio Marchionne was replaced after leading the charge to completely turn around two flagging automobile brands. Per the New York Times, the 66-year-old has become gravely ill since the July 5 surgery. Marchionne has been replaced effective immediately by Mike Manley, who was previously the company's head of North America operations. "Fiat Chrysler Automobiles N.V. communicates with profound sorrow that during the course of this week unexpected complications arose while Mr. Marchionne was recovering," the the official statement read. "These have worsened significantly in recent hours."
CNBC has a letter sent out by company president John Elkann to employees breaking the news, one he calls "without a doubt the most difficult" he's ever written. "Sergio has been the best CEO that anyone could ask for and, to me personally, a true mentor, partner and close friend," read the thoroughly praiseful note. In addition to his apparent personal magnetism, Marchionne was a measurable phenom. Under his guidance, Fiat's market value grew from $7.5 billion to about $71.5 billion. That massive growth was helped along by Fiat's daring 2009 merger with flagging American automaker Chrysler. Marchionne is credited with revitalizing both companies and his legacy is one Elkann says should be admired across the corporate world. "Sergio’s definition of a leader is truer today than ever," he wrote. "What really matters is the kind of culture he leaves behind." (Read more Fiat stories.)