Frank Kameny's Tuesday death at the age of 86 is being mourned by gay rights groups and lawmakers.

Authorities believed Kameny died in his sleep of natural causes in his Washington home. He died on the day the country celebrates National Coming Out Day.

Kameny, who was fired in 1957 by the United States government because he was gay, co-founded the Mattachine Society of Washington, one of America's earliest gay rights groups. He went on to coin the phrase “Gay is good.”

“Frank Kameny led an extraordinary life marked by heroic activism that set a path for the modern LGBT civil rights movement,” said Joe Solmonese, president of the Human Rights Campaign (HRC), the nation's largest gay rights advocate. “From his early days fighting institutionalized discrimination in the federal workforce, Dr. Kameny taught us all that 'Gay is Good.' As we say goodbye to this trailblazer on National Coming Out Day, we remember the remarkable power we all have to change the world by living our lives like Frank – openly, honestly and authentically.”

Mike Thompson, acting president of the Gay and Lesbian Alliance Against Defamation (GLAAD), said the legacy of Kameny's work lives on.

“Frank Kameny sparked national change and set the example for gay and lesbian Americans to live their lives openly and proudly. He taught us the power that our visibility and stories have in changing hearts and minds. Today on National Coming Out Day, we honor Frank's legacy not only by remembering this pioneer, but by continuing his work to speak out and share our own stories.”

Chad Griffin, board president of the American Foundation for Equal Rights (AFER), the group challenging the constitutionality of Proposition 8, California's gay marriage ban, called Kameny an American hero.

“America has lost a hero today,” Griffin wrote in a statement. “Out and proud, Frank Kameny was fighting for equality long before the rest of us knew we could. Because there was one Frank Kameny, trailblazing and honest enough to speak out 50 years ago, there are now millions of Americans, coming out, speaking out and fighting for their basic civil rights. His is a legacy of bravery and tremendous impact and will live on in the hearts and minds of every American who values equality and justice.”

House Minority Leader Nancy Pelosi added: “He turned his personal story of discrimination into action, his encounter with prejudice into determination. Through his work, he became a revered figure in the national LGBT movement; through his achievements, America became a more equal, more compassionate nation.”

(Related: White House calls Frank Kameny an American hero.)