The Pittsburgh Steelers announced Thursday that owner and longtime chairman Dan Rooney, who spearheaded the NFL's diversity efforts for decades, has died at the age of 84. His cause of death remains unknown as of now. Steelers Owner Dan Rooney Dies At 84; Tributes Rooney first began working for the Steelers — a team his family has controlled since 1933 — as a water-boy when he was 12 years old. He then joined the front office after graduating from Duquesne University in 1955. After that, Rooney served as general manager and ran the day-to-day operations of the organization from 1975 to 2003 when his son, Art Rooney Jr., took over his responsibilities. Along with the Maras, who own the New York Giants, the Rooneys are considered the first family of the NFL. The Steelers became a strong team after the NFL-AFL merger was announced in 1966. In the 1970s, Pittsburgh became a football powerhouse, as the Steelers went on to win six straight AFC Central titles to close out that decade, in addition to winning three Super Bowl titles. In total, the Steelers won four Super Bowls in six years during that time thanks to players like Terry Bradshaw, Jack Ham and Franco Harris, as well as head coaches like Chuck Noll. Several prominent members of the NFL community released statements or took to social media to praise Rooney and offer their condolences to his family and friends. "Few men have contributed as much to the National Football League as Dan Rooney," NFL Commissioner Roger Goodell wrote in a statement. "A member of the Pro Football Hall of Fame, he was one of the finest men in the history of our game and it was a privilege to work alongside him for so many years. Dan’s dedication to the game, to the players and coaches, to his beloved Pittsburgh, and to Steelers fans everywhere was unparalleled. He was a role model and trusted colleague to commissioners since Bert Bell, countless NFL owners, and so many others in and out of the NFL. A voice of reason on a wide range of topics, including diversity and labor relations, Dan always had the league’s best interests at heart. For my part, Dan’s friendship and counsel were both inspiring and irreplaceable. My heart goes out to Patricia, Art, and the entire Rooney family on the loss of this extraordinary man." In his later years, Rooney became influential in many NFL circles, and also gained a strong reputation for striving to make the league more diverse. He was even appointed as ambassador of Ireland by President Obama in 2009, and held the position until 2012. There was even a rule named after him, the "Rooney Rule," established in 2013. The rule mandated that teams interview minorities for head coaching positions and senior football operations vacancies. The rule was expanded in 2016 to include women for executive opportunities. "In the past, we've had some that were just token interviews," Rooney told USA TODAY Sports in May 2013. "They talked to someone on their staff for two minutes and said, 'Ok.' This hasn't been happening now. So I don't think you can get all excited over (backlash from) one year." Thanks to his efforts, seventeen minority head coaches were hired from 2003 through 2017, more than twice the number hired since the NFL was founded in 1920. There are now eight minority coaches in the league, including Steelers coach Mike Tomlin, who is African-American. Here are several reactions to Rooney's death, from members of the Steelers organization and all around the NFL: RIP Dan. My Mentor & friend. Thank you for your Guidance & Wisdom. I came a Young Coach & left a Better Man. Your spirit will live forever. — Bill Cowher (@CowherCBS) April 13, 2017 Sad day for anyone who's ever ran into Mr. Rooney. What a guy! He will truly be missed. He was the Steelers and Pittsburgh. ?? — Ramon Foster (@RamonFoster) April 13, 2017 Thank u Mr. Rooney! Your legacy will go on. Ive been blessed 2 have the opportunity 2 know & speak w/ u. Steelers would not b the same w/o u pic.twitter.com/1cppfRINhg — Cam Heyward (@CamHeyward) April 13, 2017 Pops ❤️you... pic.twitter.com/GgoIfmbxZH — Ike Taylor (@Ike_SwagginU) April 13, 2017 R.I.P. To Mr. Rooney. Thank you for all the knowledge you gave and support. You will always be… https://t.co/DO0BemTR1y — Ryan Shazier (@RyanShazier) April 13, 2017 Today we lost a great one! I wouldn't be a Steeler if it wasn't for Mr Rooney! We will miss you dearly! Love you DMR! -- Ben pic.twitter.com/94jtHKKeFO — BigBen7.com (@_BigBen7) April 13, 2017 I had the honor and privilege to work for two of the classiest men football has ever known. Mr Hunt and Mr Rooney God Bless & RIP Mr Rooney — Bruce Arians (@BruceArians) April 13, 2017 https://www.instagram.com/p/BS1up8jATTV/ We've lost the heart & soul of Steeler Nation. Incredible person humanitarian & true patriot. May his memory be eternal. Love U PapaRooney — Troy Polamalu (@tpolamalu) April 13, 2017 Cleary, Rooney was beloved by many, and was even a father figure to many NFL players. NEW YORK, NY - MARCH 07: Former United States Ambassador to Ireland and honoree Dan Rooney speaks onstage at the Jackie Robinson Foundation annual awards dinner on March 7, 2016 in New York City. (Photo by Craig Barritt/Getty Images for Jackie Robinson Foundation)