Bill Richardson, a former Democratic governor of New Mexico and U.S. ambassador to the United Nations, died Saturday at the age of 75, according to the Richardson Center for Global Engagement.

The center reportedly said that Richardson died in his sleep at his home in Chatham, Massachusetts.

He lived his entire life in the service of others including both his time in government and his subsequent career helping to free people held hostage or wrongfully detained abroad, said Mickey Bergman, vice president for the organization.

There was no person that Governor Richardson would not speak with if it held the promise of returning a person to freedom. The world has lost a champion for those held unjustly abroad and I have lost a mentor and a dear friend.

Richardson was born in Pasadena, California, in 1947, the son of a bank executive father and Mexican-born mother.

Last month, he was nominated for a Nobel Peace Prize for his decades of work as an international crisis negotiator, a role he continued to play even while serving two terms as governor of New Mexico from 2003 to 2011. Prior to his governorship, Richardson represented the state in Congress. He also served as President Bill Clintons U.N. ambassador and, later, his energy secretary.

More recently, Richardson worked to secure the release of WNBA star Brittney Griner, who was held captive in Russia for about 10 months until her release was announced in December.

Throughout his career, Richardson also helped secure the release of Americans in Iraq, North Korea , Sudan, Colombia and Bangladesh.

His nonprofit Richardson Center was created to promote international dialogue.

While Richardson put his hat in the ring for the 2008 Democratic presidential nomination, he dropped out to endorse Barack Obama . A few years later, he became swept up in accusations of violating campaign finance law by allegedly paying off a woman with whom hed supposedly had an affair, but no charges were filed .