As reported by the New York Times, Buckel's suicide note explained that in recent years the attorney had been moved by environmental causes.
"Honorable goal in life invites honorable objective in death", he wrote.
In a suicide note emailed to the newspaper and several other media outlets, Buckel wrote that he had used fossil fuel to symbolize what was happening to the planet.
"I hope they are at peace", Stawicki said. Part of the note reads: "Pollution ravages our planet [.] most humans breathe air made unhealthy by fossil fuels and many die early deaths as a result".
He also led Lambda Legal's work to secure justice in the Brandon v County of Richardson case, which concerned the rape and murder of transgender man Brandon Teena by two known criminals after a Nevada sheriff failed to intervene.
The case attracted quite a lot of publicity and was even adapted into a movie, concentrating on Teena's life named "Boys Don't Cry", which won actress Hillary Swank an Academy Award.
Buckel makes arguments in favor of gay marriage, Wednesday, Feb. 15, 2006, during oral arguments seeking marriage for same sex couples at the New Jersey Supreme Court in Trenton, N.J.
Friends said that after he left the organization, Mr. Buckel became involved in environmental causes, which he alluded to in his note as the reason he made a decision to end his life by self-immolation with fossil fuels.
Environmental advocate dies after setting himself on fire in NY park
Camilla Taylor, director of Lambda Legal, said in a statement to HuffPost that their organization will honor Buckel's life by "continuing to fight for equality". He was an urban gardener at the Brooklyn Botanic Garden, running a large-scale composting operation.
"I am David Buckel, and I just killed myself by fire as a protest suicide". "Our hearts go out to all who knew David".
Buckel said he wanted his death to lead to increased action, writing: "Honourable goal in life invites honourable objective in death".
"Here is a hope that giving a life might bring some attention to the need for expanded actions, and help others give a voice to our home, and Earth is heard".
"The news of David's death is heartbreaking", Taylor said.
He had recently worked with several environmental groups, according to HuffPost, including volunteering with the Added Value Red Hook Community Farm.
Some of his other more prolific cases include arguing against the Boys Scouts of America's ban on homosexual members, fighting for the creation of an LGBTQ club at a high school in Utah and helping a Pennsylvania woman win a lawsuit over being allowed to put "beloved life partner" as an epitaph over her deceased partner.
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Relatives of the Thottapilly family positively identified the items as belongings of their family members, authorities said. They had been traveling south from OR along Highway 101 when the incident occurred, officials said.