In the days since the Working Families Party endorsed Senator Elizabeth Warren for President on Monday, staffers at the progressive group have received hundreds of furious messages, including several using racial slurs against black staffers and at least one celebrating a junior employee’s rape. Maurice Mitchell, the National Director of the Working Families Party (WFP) and an organizer with the Movement for Black Lives, received messages calling him a “half man” and “Uncle Tom,” and telling him to “go back to his slave masters,” according to emails and tweets reviewed by TIME. WFP organizer Ember Ollom, a rape survivor who has tweeted about her assault, received a message that said: “We were raped by this process, so I’m happy it happened to you.” When Ollom tweeted about the harassment, more people responded to tell her she was lying. Staffers also received messages and tweets that vowed to “hunt all WFP down” and said “may you all get cancer.” One staffer received a threat that someone would find where she lived. The backlash began after the party, which has an organizing presence in 20 states and is on the ballot in three, endorsed Warren’s 2020 bid on Monday after endorsing Sanders in 2016.