A prominent gay rights lawyer and environmental advocate has burned himself to death in New York on Saturday, reportedly using fossil fuel in a protest against ecological destruction.

The charred remains of 60-year-old David Buckel were found by passers-by in Brooklyn’s Prospect Park. Police said he was pronounced dead at about 6.30am.

The New York Times said it received an emailed copy of the note, which said: “Most humans on the planet now breathe air made unhealthy by fossil fuels, and many die early deaths as a result – my early death by fossil fuel reflects what we are doing to ourselves.”

The Daily News reported Buckel left a suicide note in a shopping cart near his body that said he hoped his death was “honorable” and “might serve others”. In the note, Buckel said “I just killed myself by fire as a protest suicide”, the News reported.

Buckel was the lead attorney in a lawsuit regarding Brandon Teena, a transgender man who was murdered in Nebraska. Hilary Swank won an Academy Award for her portrayal of Teena in the 1999 film Boys Don’t Cry.

Hilary Swank as Brandon Teena in Boys Don’t Cry. Photograph: Allstar/20th Century Fox

Buckel also served as marriage project director at Lambda Legal, a national organisation that fights for LGBT rights, where he was the strategist behind same-sex marriage cases in New Jersey and Iowa.

Susan Sommer, a former Lambda Legal lawyer who is now the general counsel for the mayor’s office of criminal justice in New York, told the Times Buckel “was all about justice, but he was also all about what it means to be human”.

Sommer added: “He was a very smart and methodical lawyer. He knew his craft and his trade and was strategic in how to build the blocks toward a sweeping victory.”

• In the UK the Samaritans can be contacted on 116 123. In the US, the National Suicide Prevention Lifeline is 1-800-273-8255. In Australia, the crisis support service Lifeline is 13 11 14. Other international suicide helplines can be found at www.befrienders.org.