After NASA announced on Thursday that the first African-American slated to be on the International Space Station was no longer part of the mission, the agency faced a massive public backlash and calls for the decision to be reversed.

Jeanette Epps would have made history if she’d been able to go up on the June mission. Instead, she will be replaced by Serena Auñón-Chancellor, who was selected with Epps as an astronaut in 2009.

“Serena Auñón-Chancellor, who previously was assigned to Expedition 58/59, has been reassigned to the Expedition 56/57 crew, launching in June. She is taking the place of astronaut Jeanette Epps, who will return to NASA’s Johnson Space Center in Houston to assume duties in the Astronaut Office and be considered for assignment to future missions,” NASA said, in part, in a statement announcing the decision.

Accusations of racism

The decision regarding Jeannette Epps drew heavy criticism, especially because there reportedly was no explanation for the move. And some people, like Epps’ own brother, believe that her race was a major factor.

“My sister Dr. Jeannette Epps has been fighting against oppressive racism and misogynist in NASA and now they are holding her back and allowing a Caucasian Astronaut to take her place!” Henry Epps wrote in a Facebook post that has since been deleted.

He also decried the environment of racism in the Trump administration.

“My sister deserve a chance just life [sic] her white peers! This administration policies and culture is reprehensible against their stance against women and minorities in this nation. We have lost all of the gains we gained over the past 40 years in one year? No more. We cannot continue to tolerate what is going on in America but we must stand together and stand behind our people and out [sic] nation!” he wrote.

Henry Epps also shared a petition on Facebook several times that demanded NASA reinstate his sister to the mission.

As of Monday evening, the MoveOn.org petition had more than 1,200 signatures.

Many commenters on the petition called for NASA to at least account for their decision surrounding Jeannette Epps and give an explanation.