The 48-year-old Bell had been an umpire since 1993 and was a part of the crew in the National League Division Series in which the St Louis Cardinals beat the Pittsburgh Pirates in a Game Five decider last week.
Baseball made the shocking announcement on the same day the Los Angeles Dodgers battled the Cardinals in Game Three of the National League Championship Series, adding a sombre mood to the contest for the officiating crew.
"I give these guys a lot of credit because there was a ton of emotion in that umpire's room," MLB executive vice president Joe Torre said following the contest.
"It hits you right between the eyes."
Bell, who is survived by a teenage son and daughter, was on the World Series umpiring crew in 2006 and he worked the 1997, 2000 and 2013 All-Star Games.
In 11 other seasons, including 2013, he worked in a league championship series or a division series.
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