Grace Rebecca Mann (Courtesy of Grace Rebecca Mann's family)

A University of Mary Washington student allegedly killed by her roommate had an altercation with him before her death and received numerous calls and text messages from him, according to a search warrant.

Grace Rebecca Mann, 20, of McLean, was also threatened with rape by an anonymous poster on the social networking app Yik Yak and she feared for her safety in the month before her slaying, according to a friend who saw the message.

The revelations came Thursday as Mann’s feminist group at Mary Washington announced it was filing a federal complaint accusing the school of doing little to combat a flood of violent and sexual threats against members on Yik Yak this year. School officials denied the charges.

Members said they felt afraid on campus, resorted to carrying rape whistles, walked in groups and one sought counseling. The messages came after Feminists United members came out in opposition to bringing Greek life to campus and commented on a lewd chant at a party by members of the rugby team.

One poster wrote “Gonna tie these feminists to the radiator” and rape them. Another promised to kill “a [expletive] . . . or two” and a third called for euthanizing members, according to the complaint. There were more than 700 messages.

Fredericksburg police investigate the scene in the 1900 block of Washington Avenue in Fredericksburg on April 17, 2015. (Peter Cihelka / The Free Lance-Star/AP)

Members said the messages were especially chilling because Yik Yak functions as a virtual community bulletin board, aggregating comments from its anonymous users within a 1.5-mile radius.

“I was terrified,” said Julia Michels, president of Feminists United. “I didn’t know if the person sitting next to me in class was going to rape me.”

Michels said group members met multiple times with top university officials to express their concerns about the messages, including once a little over a week before Mann was slain on April 17. Steven Vander Briel, 30, is accused of killing Mann in the off-campus home they shared with two other students.

Authorities have not revealed a motive, and Feminists United members said they had no evidence connecting Mann’s killing to the Yik Yak threats or her activism on campus. The family said the two did not have a personal relationship and Vander Briel was simply renting a room in the house.

In a statement, university officials said they had been engaging with Feminists United and other students throughout the year to address issues of safety and campus culture. They said they take allegations of gender-based violence very seriously and would cooperate with any investigation that follows the complaint.

“Creating a safe learning and living environment is our first and foremost concern,” said Richard V. Hurley, president of the school.

Detectives filed additional search warrants in Fredericksburg Circuit Court seeking information from Vander Briel’s cellphone and a computer.

The University of Mary Washington student group "Feminists United" filed a complaint with the U.S. Department of Education, accusing the school of failing to act on online threats against its members, one of whom was killed last month. (WUSA9)

The documents said Mann’s roommates had seen her on the Mary Washington campus about 2:20 p.m. April 17 and Mann told them she was going home to do her hair before a 3 p.m. event.

When the roommates arrived home a short time later, they found Vander Briel exiting one of their rooms and closing the door behind him, which was suspicious to them, according to the search warrant.

The roommates asked where Mann was and Vander Briel told them he had an altercation with her. The search warrant does not say what sparked the altercation. Vander Briel directed the roommates to the room he had exited and they found Mann, according to the search warrant.

A previous search warrant said the roommates found Mann bound and unconscious. The roommates tried to resuscitate her as Vander Briel fled the home. Mann was taken to the hospital, where she died.

Vander Briel was arrested and charged with first-degree murder and abduction. Detectives think plastic shopping bags were used to asphyxiate Mann, according to a search warrant.

The killing ended a tumultuous year on campus.

Feminists United members had spoken out about a recording of members of the rugby team chanting about having sex with a dead prostitute. The stance caused a backlash on Yik Yak. The school suspended the team in March.

Zakaria Kronemer, Mann’s friend, said it was after that controversy that someone posted on Yik Yak that Mann would be raped at a location on campus.

“She was afraid,” Kronemer said. “She was worried about her safety.”