Hunter Harrison, the president CEO of railroad giant CSX Corp., has died, the company announced Saturday. He was 73.

CSX confirmed Harrison's death in a statement, saying it was caused by "unexpectedly severe complications" from a recent illness. His death in Wellington, Fla., comes only a couple days after the company announced he was taking an unplanned medical leave of absence.

Born in Memphis, Tenn., Harrison was a long-time railroad executive who made his career turning around railroads. Before joining CSX in March, Harrison was president and CEO of Canadian Pacific Railway and the Canadian National. He also was the head of the Illinois Central Railway in the 1990s.

He was credited with generating significant profits at both Canadian rail companies by employing tighter train schedules and lean expenses through a management philosophy known as "precision scheduled railroading."

"Hunter was a larger-than-life figure who brought his remarkable passion, experience and energy in railroading to CSX," the company said in a statement.

Recent health concerns

He was hired by Florida-based CSX in March under shareholder pressure. But recently there had been concerns about his health. The Wall Street Journal reported in May that Harrison often worked from home and occasionally required portable oxygen.

CSX shares fell sharply on Thursday when the company announced Harrison was taking the unexpected leave of absence.

Edward Kelly, chairman of CSX's board of directors said that Jim Foote, who was named acting CEO when Harrison took the leave of absence, will continue in his acting CEO role. Kelly called Harrison's death "a major loss" to the company but said they would try to implement some of the ideas Harrison had for the railroad before his death.