Silverman became the religious right’s favorite godless bogeyman, sparring with presenters on Fox News after launching billboard campaigns urging people to skip church and telling them that Christmas is a myth. In another stunt, he applied in New Jersey for the vehicle license plate “ATHE1ST,” which was denied for being “objectionable.”

Silverman became president of American Atheists in 2010 and helped raise the organization’s profile. In 2012, he organized the Reason Rally in Washington, DC, which brought thousands of atheists to the National Mall to hear speeches promoting secularism from celebrities, including evolutionary biologist Richard Dawkins, comedian Eddie Izzard, and MythBusters cohost Adam Savage.

In a brief statement to BuzzFeed News, Silverman’s lawyer, Sebastian Ionno, said that “Mr. Silverman denies any wrong doing and has never had a non-consensual sexual encounter.” At the time of the alleged incidents, he added, Silverman and his wife were in an open marriage.

“Last night, the American Atheists Board of Directors voted to terminate David Silverman as President of American Atheists,” the group said in a statement released Friday. The board made its decision after reviewing “allegations raised regarding Mr. Silverman’s conduct,” the statement said. The board also said it intends to cooperate with any future investigations.

The group’s board held an emergency meeting Thursday evening and unanimously voted to fire 51-year-old Silverman, based on explosive written allegations of sexual assault and undisclosed conflicts of interest, BuzzFeed News has learned.

David Silverman, a firebrand atheist with a knack for generating publicity for his cause, has been abruptly fired as president of American Atheists, one of the leading secular organizations in the US.

On Tuesday, American Atheists placed Silverman on paid leave while it investigated a complaint from staff concerned that he had not disclosed financial and personal conflicts of interest relating to the promotion of his book, Fighting God: An Atheist Manifesto for a Religious World, and the appointment to a senior position of a woman with whom Silverman was allegedly having a sexual relationship. (That appointment has been rescinded.)

After word spread about the investigation, American Atheists received additional written complaints about two allegations of sexual misconduct involving Silverman.

Like many other communities in the #MeToo era, the atheist movement is undergoing a reckoning over the treatment of women in its ranks. In February, BuzzFeed News exposed allegations of sexual harassment against another prominent atheist, the physicist Lawrence Krauss. In the wake of that story, two women told BuzzFeed News that they were assaulted by Silverman. They each filed written complaints to American Atheists this week.

In one of those complaints, a woman described a hotel room party held at the end of the 2015 American Atheists Convention in Memphis. She used her name in the confidential complaint, but because of concerns about hostility experienced by other women who have made allegations of sexual misconduct against prominent atheists, she asked BuzzFeed News to use her first initial, R.

She and Silverman had known each other for years, and he flirted with her throughout the evening, she wrote in the complaint. After the other guests left, R. wrote that Silverman asked her to join him in smoking marijuana on the roof. But before they left the room, he suddenly forced himself on her.

“He physically pressed me to the wall and began to kiss me forcefully, grabbed my breasts, and put his hand into my leggings where there was actual penetration of my vagina,” she wrote.

R. believed Silverman knew she was interested in BDSM and wrote that he began using insulting language, calling her a “dirty little whore.” He then pushed her to her knees, “where his penis briefly made contact with my mouth,” she wrote.

R. got her feet and said “no,” she wrote. Silverman then lightly slapped her face and said, "You don't get to say no to me."

At that point, R. said the widely used BDSM safe word, “red,” which stopped him, and then she left. The next day, R. took photographs of bruises where she said Silverman had grasped her, and these pictures were included in her complaint to American Atheists.

Two prominent atheists confirmed to BuzzFeed News that R. told them about the incident in the days after it happened.

Greta Christina, a blogger and speaker, said that R. was extremely distressed. “It became very clear to me it was a case of sexual assault," Christina said. Heina Dadabhoy, who is known in atheist circles for speaking about leaving Islam to join the movement, said that they woke up the morning after the incident to find a series of distressed Facebook messages from R., and immediately contacted her. (BuzzFeed News has reviewed the messages.) “I was just trying to comfort her and talk her through it," Dadabhoy said.

R. told BuzzFeed News that she did not complain to American Atheists at the time because she was worried that her reputation would be attacked, given Silverman’s power within the movement. She decided to tell the organization this week after learning that it was investigating him.

The third allegation reviewed by the American Atheists board involves a student, Rose St. Clair, who alleged that Silverman used his position of power to pressure her into having sex with him. “At several points during this encounter, I hesitated to continue,” she wrote. “I believed that if I did anything to upset him, my chances at being involved in the secular community, especially with American Atheists, would be ruined.”

In 2012, St. Clair was an undergraduate at the College of William and Mary in Virginia who hoped to make a career in the atheist movement. At the annual convention of the Secular Student Alliance in Columbus, Ohio, she was invited to go to a bar with a group of speakers at the conference, including Silverman.