More specifically, MLB.com's Barry Bloom reports Gwynn passed away due to salivary gland cancer:
"Hall of Famer Tony Gwynn, the greatest Padres player and arguably the best Major League hitter of the latter part of the 20th century, passed away early Monday morning at Pomerado Hospital in Poway, Calif., surrounded by his family. Gwynn, who was 54, had been battling salivary gland cancer.
"Gwynn's .338 career batting average over 20 seasons -- all of them with the Padres -- is the highest since Ted Williams retired from the Red Sox in 1960 with a .344 average. Gwynn's playing career ended in 2001, and since then he had been the head baseball coach for San Diego State University, where he starred in both baseball and basketball as a collegian, and a part-time analyst on Padres telecasts.
"Gwynn had been on medical leave from his head coach position at San Diego State since March and had signed a one-year extension on Wednesday.
"'Mr. Padre' won a record eight National League batting titles -- equal to the number won by Honus Wagner -- and collected 3,141 hits in his career, 19th all time. He was inducted into the Hall of Fame in 2007 along with Orioles great Cal Ripken in front of an estimated 75,000 people in Cooperstown, N.Y.
"Major League Baseball today mourns the tragic loss of Tony Gwynn, the greatest Padre ever and one of the most accomplished hitters that our game has ever known, whose all-around excellence on the field was surpassed by his exuberant personality and genial disposition in life,' Commissioner Bud Selig said in a statement.
"'Tony was synonymous with San Diego Padres baseball, and with his .338 career batting average and eight batting titles, he led his beloved ballclub to its greatest heights, including two National League pennants.
"'Tony loved our game, the city of San Diego and his alma mater where he starred and coached, San Diego State University, and he was part of a wonderful baseball family. His commitment to the children of San Diego made him a deserving recipient of our game's highest off-field honor, the Roberto Clemente Award, in 1999.
"'For more than 30 years, Tony Gwynn was a source of universal goodwill in the national pastime, and he will be deeply missed by the many people he touched. On behalf of all our clubs, I extend my deepest condolences to Tony's wife Alicia, their son Tony, Jr. of the Phillies, their daughter Anisha, the Padres franchise, his fans in San Diego and his many admirers throughout baseball.'
"Gwynn's battle with cancer began in 2009 when a malignant tumor was removed from his right cheek. Gwynn claimed that the cancer in the salivary gland was the result of his longtime habit of chewing tobacco. The cancer returned twice, and in the latter part of '12, he again began radiation treatment in an attempt to shrink the tumor.
"Gwynn underwent another round of surgery in early 2012 when the nerve that the tumor was wrapped around had to be replaced with one from his shoulder. In each case, Gwynn valiantly fought back."
ESPN added more details about Gwynn's passing:
"He had two operations for cancer in his right cheek between August 2010 and February 2012. The second surgery was complicated, with surgerons removing a facial nerve because it was intertwined with a tumor inside his right cheek. They grafted a nerve from Gwynn's neck to help him eventually regain facial movement.
"Gwynn had said he believed the cancer was from chewing tobacco.
"'He was in a tough battle and the thing I can critique is he's definitely in a better place,' longtime agent John Boggs told The Associated Press. 'He suffered a lot. He battled. That's probably the best way I can describe his fight against this illness he had, and he was courageous until the end.'
"In a rarity in pro sports, Gwynn spent his entire 20-year career with the Padres, choosing to stay rather than leaving for bigger paychecks elsewhere. His terrific hand-eye coordination made him one of the game's greatest contact hitters.
"He excelled at hitting singles the other way, through the '5.5 hole' between third base and shortstop.
"'There are no words to express what Tony means to this organization and this community,' the Padres said in a statement. 'More than just Mr. Padre, Tony was Mr. San Diego. He cared deeply about our city and had a profound impact on our community.
"'He forever will be remembered not only for his tremendous on-field accomplishments, but also for his infectious laugh, warm, outgoing personality and huge heart. On behalf of Padres fans everywhere, we mourn the loss of a friend, a teammate and a legend.'"
Rest in peace, Mr. Padre.