David S. Buckel, a prominent attorney who championed LGBT rights, died Saturday in an apparent protest suicide. He was 60.

Buckel's burned body was found by a passerby in Brooklyn's Prospect Park, The New York Times reported. A manila envelope marked “To the police” included a note outlining Buckel's protest. The note was also emailed to the Times.

“Pollution ravages our planet, oozing inhabitability via air, soil, water and weather,” the note stated. “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.”

Many friends told the Times that Buckel had become an environmental activist in recent years.

As marriage project director at Lambda Legal, Buckel helped win marriage rights for gay and lesbian couples in Iowa and New Jersey. Other notable cases involved a gay Wisconsin high school student who sued his school district for failing to protect him from bullies and a transgender man who was brutally raped and murdered after authorities failed to intervene.

“His thoughtful and engaging advocacy broke through many stubborn misconceptions and showed it was possible and necessary for our movement to speak up for bullied, ostracized LGBT young people,” Camilla Taylor, Lambda Legal's acting legal director, said in a statement.

Buckel and his partner Terry Kaelber co-parented a daughter, Hannah, with another couple, Rona Vail and Cindy Broholm.