Microsoft (MSFT - Get Report) co-founder Paul Allen passed away on Monday in Seattle from complications of non-Hodgkin's lymphoma. 

The news was announced in a statement from his investment fund, Vulcan Inc. Allen, who also owned the NFL team the Seattle Seahawks and the NBA team the Portland Trail Blazers, was one of the wealthiest people in the world, with an estimated net worth of $26.1 billion, according to Bloomberg's Billionaire's Index. That ranked him as the 27th-richest individual in the world.

Allen co-founded software giant Microsoft along with Bill Gates in 1975. The pair originally created Microsoft as an implementation of the BASIC programming language, and eventually grew the company into one of the most valuable corporations in the world. Allen left the board of Microsoft in 2000, and went on to pursue a variety of other philanthropic and business ventures spanning technology, scientific research, real estate, the arts and sports. 

Allen purchased the NBA's Trail Blazers in 1998 and the Seahawks in 1996, and was also part owner of a Major League Soccer franchise, the Seattle FC. He is credited with helping usher the Seahawks to three Super Bowl appearances. Through Vulcan Inc., Allen was also involved in a diverse range of activities including real estate development, wildlife conservation and aerospace engineering. In 2003, he launched the Allen Institute for Brian Science and donated hundreds of millions to the organization.

Vulcan CEO Bill Hilf wrote in a statement on the fund's website that Allen's life "reflected his myriad interests in technology, music and the arts, biosciences and artificial intelligence, conservation and in the power of shared experience -- in a stadium or a neighborhood -- to transform individual lives and whole communities." Vulcan's real estate division is noted as one of the most influential real estate developers in the Seattle area. 

In a statement released on Twitter, Microsoft CEO Satya Nadella called Allen's contributions to the company and the industry "indispensable." 

Statement from Microsoft CEO Satya Nadella on the passing of Paul Allen:

— Microsoft (@Microsoft) October 15, 2018 

Former Microsoft CEO Steve Ballmer also tweeted about what Allen meant to him.

Paul was a truly wonderful, bright and inspiring person—- and a great friend. I will miss him

— Steve Ballmer (@Steven_Ballmer) October 15, 2018

I also want to add that Paul's insights were critical to the creation and success of Microsoft. He was a great professional mentor and teacher for me.

— Steve Ballmer (@Steven_Ballmer) October 16, 2018

Many current tech leaders, including Apple Inc. (AAPL - Get Report) CEO Tim Cook and Alphabet's (GOOGL - Get Report) Google CEO Sundar Pichai, also tweeted their condolences. 

Our industry has lost a pioneer and our world has lost a force for good. We send our deepest condolences to Paul's friends, the Allen family and everyone at Microsoft.

— Tim Cook (@tim_cook) October 15, 2018

We lost a great technology pioneer today - thank you Paul Allen for your immense contributions to the world through your work and your philanthropy. Thoughts are with his family and the entire Microsoft community.

— Sundar Pichai (@sundarpichai) October 15, 2018

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