CHATHAM, MASSACHUSETTS: Bill Richardson, the former New Mexico governor and US ambassador to the UN, has died at the age of 75 in his sleep.

The Richardson Center for Global Engagement, an organization he established and headed, announced he had died in his home in Chatham, Massachusetts, per the Daily Mail.

"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," the center's vice-president Mickey Bergman said.

He further said, "There was no person that Gov. Richardson would not speak with if it held the promise of returning a person to freedom."

He added, "The world has lost a champion for those held unjustly abroad and I have lost a mentor and a dear friend."

Who was Bill Richardson?

Richardson, who would become governor in 2002, held significant positions in the government before his term as governor. He served as the UN ambassador and energy secretary under President Bill Clinton.

He also represented northern New Mexico as a congressman for 14 years.

Richardson established a reputation as an unofficial diplomatic troubleshooter, undertaking global missions to negotiate the release of hostages and American servicemen from countries such as North Korea, Iraq, Cuba and Sudan.

Richardson was known for negotiating with America's adversaries, including Saddam Hussein, and humorously called himself "the informal undersecretary for thugs."

He ran for president in 2008 on a Democratic ticket, aiming to become the first Hispanic president. However, he dropped out of the race after coming in fourth in the Iowa caucuses and the New Hampshire primary.

Richardson served as the nation's only Hispanic governor during his two terms in office. He described being governor as "the best job I ever had. It's the most fun. You can get the most done. You set the agenda."

As governor, Richardson signed legislation in 2009 that repealed the death penalty, a decision he described as the "most difficult in my political life" due to his prior support for capital punishment.

Following his political career, he dedicated himself to the mission of securing the release of Americans detained overseas, which notably included WNBA player Brittney Griner.

He was nominated for a Nobel Peace Prize in August.

Bill Richardson played major role in Brittney Griner's release

Richardson played a big role in getting basketball player Griner released. She was held in Russia for nearly 10 months in 2022 because of vape canisters with cannabis.

She got a nine-year prison sentence in Russia but was freed in December 2022. The US sent Viktor Bout, a weapons dealer, back to Russia in exchange for her release.