Larry Kramer, the writer and influential gay activist who pressed the U.S. government and the medical establishment to respond to the AIDS epidemic, has died. He was 84.

Kramer died Wednesday from pneumonia, his husband David Webster told the New York Times.

Earlier in his life, Kramer was a screenwriter with credits including “Women in Love” and the 1973 musical “Lost Horizon.”

Spurred by the onset of the AIDS epidemic in the early 1980s, Kramer became a fierce activist and an impassioned writer, and one of the earliest and most vocal advocates for AIDS research, treatment access and institutional recognition of the gay community so hard-hit by the disease. He is best known not only as one of the founders of both Gay Men’s Health Crisis and ACT UP, but also as the writer of novels and plays including his 1985 work “The Normal Heart,” his urgent, agitprop depiction of the early days of the AIDS crisis.

A prominent and contentious voice in the gay community, Kramer fearlessly put forth hard truths and controversial opinions, as when, in a 1983 editorial, he urged gay men to stop having sex until more was known about AIDS and how it spread.

Later in life, Kramer rode a wave of recognition for his accomplishments. A 2011 Broadway revival of “The Normal Heart” won three Tonys, and Kramer picked up a 2013 special Tony for his contribution to humanitarian causes. Ryan Murphy’s movie adaptation of “Normal Heart,” which starred Mark Ruffalo and Julia Roberts, aired on HBO in 2014 and earned two Emmys.

The first half of his epic, fictionalized take on U.S. history, “The American People,” was released in March 2015. HBO, which aired documentary “Larry Kramer: In Love and Anger” in June 2015, commissioned a film sequel to “The Normal Heart,” which Kramer told Variety would chart the time period between the end of “Normal Heart” in 1984 and the appearance of the first HIV drugs in 2001.

Fiercely confrontational in public but privately shy and sensitive, Kramer began his career in the movie business. After attending Yale and then doing a stint in the Army, he worked for Columbia Pictures and then United Artists on films ranging from “Dr. Strangelove,” “Bridge Over the River Kwai” and “Suddenly, Last Summer.” In 1969 he received his first major writing credit on Ken Russell’s “Women in Love,” which included an attention-getting scene in which Alan Bates and Oliver Reed wrestle nude. Kramer was nominated for an Oscar for the screenplay.

The success of “Women in Love” led to Columbia to hire Kramer to write the screenplay for “Lost Horizon,” a big-budget musical fantasy set in Shangri-La. The 1973 movie proved a major flop, but the hefty fee Kramer commanded on the film allowed him to concentrate full time on writing novels and plays that could address the gay themes that were his passion.

His 1978 novel “Faggots” aimed to depict love, life and sex among the gay men of New York and Fire Island, but on its release caused a furor among readers and critics, with the gay community in particular deriding the novel for what was perceived as a negative depiction of gay life.

In 1980 and ’81, as his friends and colleagues began to sicken with what was then a mysterious illness, Kramer became one of the earliest leaders in the movement for AIDS treatment and research. He co-founded Gay Men’s Health Crisis, but his belligerent tactics — openly blaming Ronald Reagan, Ed Koch and New York Times chief A.M. Rosenthal for what he insistently called the AIDS plague — caused a split with the group.

He expressed his frustration over the divide in “The Normal Heart,” which premiered at Off Broadway’s Public Theater in 1985. His depiction of the himself, in the thinly veiled character of the impassioned and combative protagonist Ned Weeks, proved he could be as lacerating a critic of himself as he was of others. “I wasn’t trying to present myself as a hero,” he said in the HBO documentary. “I was trying to present myself as a pain in the ass.”

In 1987 he co-founded civil disobedience movement ACT UP, continuing his activist work while writing plays including “Just Say No, A Play About a Farce” and “The Destiny of Me,” a 1992 sequel to “The Normal Heart” that starred John Cameron Mitchell. His books include “Reports From the Holocaust: The Story of an AIDS Activist” and “The Tragedy of Today’s Gays.”

Kramer was born in Bridgeport, Connecticut, to an attorney father and social worker mother. Kramer described his childhood as an unhappy one, particular in his relationship with his father, but his brother, attorney Arthur Kramer, was a beloved and hugely important figure to Kramer despite their disagreements.

Beginning in 2013, Kramer spent months in the hospital recovering from complications from a liver transplant brought on by years of battling HIV. In 2013 he married his longtime partner, David Webster, from his hospital bed, in a real-life scene that mirrored the final moments of “The Normal Heart.” He was released in 2014, continuing to write and appearing at the 2014 Emmy Awards.

Kramer was never one to rest on his laurels. When asked in a 2013 interview with Variety to consider whether art works as activism, Kramer responded, “Who in hell knows?” and cited statistics that, despite the victories of GMHC and ACT UP, HIV infection rates were on the rise among young men. During the Broadway run of “Normal Heart,” Kramer could be found in front of the theater handing out fliers and stirring up awareness among exiting patrons.

And although he became best-known for the work he did after leaving Hollywood, show business remained a significant influence in all of his work. “The analogy is really with the movie business,” he said of the civil disobedience events he staged (speaking in documentary “Larry Kramer in Love and Anger”). “I was trained in the movie business. You call it direct action, I call it putting on a show.”