Fifteen years ago Monday, Pat Tillman, the Arizona Cardinals safety who walked away from the NFL to join the U.S. Army, was killed in Afghanistan.

The Cardinals and NFL are among those remembering Tillman on social media:

Today we remember the life and legacy of Pat Tillman, who lost his life 15 years ago. 🇺🇸 pic.twitter.com/3XliavoOeO — Arizona Cardinals (@AZCardinals) April 22, 2019 We lost a true hero 15 years ago today.



Rest in peace, Pat Tillman. 🙏 pic.twitter.com/ITPKwzzysy — NFL (@NFL) April 22, 2019

Tillman was the oldest of three brothers; on May 31, 2002, Tillman and one of his two younger brothers, Kevin, signed up for the Army in response to the 9/11 attacks nearly a year earlier.

Pat had played incredibly well in 2000 and 2001, and Kevin was part of the Cleveland Indians’ farm system; the two left behind their respective sports careers to enlist, and after basic training were accepted into the elite Army Rangers.

After graduating from Ranger School in November 2003, Pat Tillman was deployed to Afghanistan and Forward Operating Base Salerno. Less than five months later, he was killed.

Tillman was just 27.

15 PHOTOS Pat Tillman's NFL career, death See Gallery Pat Tillman's NFL career, death Former NFL star and U.S. Soldier Pat Tillman is pictured in this June 2003 file photograph. The Pentagon's inspector general will blame nine U.S. Army officers, including up to four generals, for missteps after the April 2004 death in Afghanistan by friendly fire of Tillman, the "CBS Evening News" reported on March 23, 2007. It said the Pentagon would release its findings on Monday, showing the officers failed to follow regulations and used poor judgment in keeping the truth of the cause of Tillman's death from his family for more than a month. REUTERS/Photography Plus C/O Stealth Media Solutions/Handout (UNITED STATES). EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. TEMPE, AZ - NOVEMBER 5: Arizona Cardinals' Rob Fredrickson (59)and Pat Tillman (40) celebrate while Washington Redskins Albert Connell sits on the ground 05 November, 2000, as the game ends. Connell failed to catch a fourth down Jeff Blake pass. The Cardinals defeated the Redskins 16-15 at Sun Devil Stadium in Tempe, Arizona. (Photo credit should read IRWIN R. DAUGHERTY/AFP/Getty Images) UNITED STATES - OCTOBER 03: Football: Arizona Cardinals Pat Tillman (40) in action, making tackle vs Dallas Cowboys Deion Sanders (21), Irving, TX 10/3/1999 (Photo by Damian Strohmeyer/Sports Illustrated/Getty Images) (SetNumber: X58821 TK2 R6 F18) CINCINNATI, OH - DECEMBER 3: Pat Tillman #40 of the Arizona Cardinals lines up against the Cincinnati Bengals at Paul Brown Stadium on December 3, 2000 in Cincinnati, Ohio. The Bengals defeated the Cardinals 24-13. (Photo by Joe Robbins/Getty Images) UNITED STATES - APRIL 24: Daily News front page dated April 24, 2004, Headline: They called him a football hero, but Pat Tillman turned down millions to fight for something he believed in. On the battlefield of Afghanistan he died a..., TRUE HERO (Photo by NY Daily News Archive via Getty Images) NEW YORK CITY - APRIL 24: A memorial for former NFL defensive back Pat Tillman during the 2004 NFL Draft on April 24, 2004 at Madison Square Garden in New York City. The 27-year-old former Arizona Cardinals football player was killed in direct action during a firefight in eastern Afghanistan two days before the draft. Tillman left the NFL shortly after the September 11th attacks and enrolled in the Army to become an Army Ranger. (Photo by Chris Trotman/Getty Images) SAN JOSE, CA - MAY 3: Darius Rucker of Hootie and the Blowfish sings at a memorial service for Pat Tillman in the Municipal Rose Garden May 3, 2004 in San Jose, California. Pat Tillman, former professional football player for the Arizona Cardinals, gave up his NFL career to enlist as an Army Ranger and was killed on patrol in Afghanistan on April 22, 2004. (Photo by Gene Lower-Pool/Getty Images) SAN JOSE, CA - MAY 3: Memorial cards are passed out at a service held by the family of Cpl. Pat Tillman for Tillman, who was killed in action in Afghanistan April 22, 2004, at the San Jose Municipal Rose Garden May 3, 2004 in San Jose, California. (Photo by David Paul Morris/Getty Images) NFL commissioner Paul Tagliabue speaks in front of a poster of former Arizona Cardinals Pat Tillman during a news conference before the memorial service for Tillman in San Jose, California, May 3, 2004. Tillman, who gave up his NFL career to enlist in the U.S. Army as a Ranger, was killed in battle in Afghanistan on April 22. REUTERS/Gene Lower/POOL PS/GAC California first lady Maria Shriver speaks at a memorial service for former Arizona Cardinal Pat Tillman in San Jose, California, May 3, 2004. Tillman, who gave up his NFL career to enlist in the U.S. Army as a Ranger, was killed in Afghanistan on April 22. REUTERS/Gene Lower/POOL PS/GAC A still image taken off a live feed of the Pentagon news conference shows a file photo of U.S. Army Ranger Cpl Pat Tillman (L), and U.S. Defense Department Acting Inspector General Thomas Gimble speaking about the circumstances surrounding Tillman's death, inside the press briefing room of the Pentagon March 26, 2007. A Pentagon watchdog on Monday found fault with nine officers for investigations and incorrect accounts of the death of U.S. Army Ranger and former professional football star Tillman in Afghanistan. REUTERS/Jason Reed (UNITED STATES) Military personnel bow their heads in moment of silence during ceremony to open Pat Tillman United Service Organizations centre at Bagram Air Base near Kabul. Military personnel bow their heads in a moment of silence during a ceremony to open the Pat Tillman United Service Organizations (USO) centre at Bagram Air Base near Kabul, Afghanistan, April 3, 2005. The National Football League donated $250,000 to the USO in 2004, named in honour of Pat Tillman, a former player with the Arizona Cardinals and a U.S. Army Ranger who was killed in Afghanistan in 2004. REUTERS/USO photo/Mike Theiler/Handout Marie Tillman, wife of former football star Pat Tillman, listens to Pat Tillman's brother Kevin Tillman (L), speak about Pat Tillman's death in battle, at a hearing titled "Misleading information from the battlefield" held by the House Oversight and Government Reform Committee on Capitol Hill in Washington April 24, 2007. Pat Tillman was killed by friendly fire in Afghanistan in 2004. REUTERS/Kevin Lamarque (UNITED STATES) The Pat Tillman memorial statue is unveiled before the Arizona Cardinals vs Dallas Cowboys game at University of Phoenix Stadium in Glendale, Arizona on November 12, 2006. (Photo by Gene Lower/Getty Images) SAN JOSE, CA - MAY 3: Zack Walz, who was Arizona Cardinals' Pat Tillman's roommate and teammate, speaks to the crowd during a memorial service for Cpl Pat Tillman on May 3, 2004 at the San Jose Municipal Rose Garden in San Jose, California. Tillman turned down a lucrative NFL contract to serve as a US Army Ranger and was killed in action in Afghanistan April 22, 2004. Walz also played against Tillman in San Jose during High School. (Photo by David Paul Morris/Getty Images) Up Next See Gallery Discover More Like This HIDE CAPTION SHOW CAPTION of SEE ALL BACK TO SLIDE

Initially, the Army reported that Tillman was killed by enemy combatants, but after an investigation it was learned that it was friendly fire. He was posthumously awarded the Purple Heart and Silver Star for his service.

Tillman is one of 2,216 American servicemen and women killed in Afghanistan as part of Operation Enduring Freedom.

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