Students, family and friends gather at the steps of George Washington Hall to honor Grace Mann's life on April 24 in Fredericksburg. (Reza A. Marvashti/For The Washington Post)

A feminist group at the University of Mary Washington is accusing school officials of failing to act on threats against its members — one of whom was killed last month — on the popular and controversial messaging app Yik Yak, an attorney for the group said.

Feminists United plans to announce at a news conference Thursday that it has filed a complaint with the U.S. Department of Education alleging that members were threatened with sexual assault and death and were cyber-stalked after speaking out in campus debates about Greek life and against a lewd chant by the rugby team this year, said attorney Lisa Banks.

Authorities say that Grace Rebecca Mann, a 20-year-old from McLean, Va., who served on United’s board, was slain April 17 by a roommate. Steven Vander Briel was charged with first-degree murder and abduction. Police have not commented on an alleged motive.

Banks and United members said they have no evidence that Mann’s activism or the threats on Yik Yak were related to her slaying. But they said a flood of more than 700 messages — some of which targeted members by name — left them feeling afraid. They said school officials did nothing to stop the threats despite repeated requests throughout the year.

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

“I felt deeply unsafe at many points,” said Paige McKinsey, the outgoing president of the university’s Feminists United group. “I made sure to walk with people. I made sure my apartment door was locked and told people where I was going.”

School officials said they acted on all threats of violence or sexual assault on the social-media site and that student safety is their top priority.

“If we receive any complaints, we investigate them and offer extra security as needed,” said school spokeswoman Anna Billingsley.

Yik Yak’s popularity has exploded on campuses nationwide since it was introduced in the fall of 2013. The app allows smartphone users within a 1.5-mile radius to post and read messages anonymously in real time, making it well-suited to campus life.

The vast majority of traffic includes gripes about finals, talk of drinking and jokes, but the app also has been a freewheeling forum for racism, misogyny and threats that have made it a lightning rod at many schools.

During the past year, at least 13 students have been arrested on charges of threatening mass shootings, bombings and other mass violence through Yik Yak. A Virginia Tech senior was arrested last month after allegedly posting a message warning of another “4.16 moment” — a reference to the date of the 2007 campus massacre in which a student killed 32 people.

After a black student at the University of Virginia was arrested by a group of white Alcoholic Beverage Control officers in March, the app was bombarded with racist comments and disparaging remarks about the victim, 20-year-old Martese Johnson. And Emory University’s student government passed a resolution denouncing the use of Yik Yak to spread hate speech and harassment.

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)

Yik Yak has said it has taken a number of steps to limit hateful speech on the app.

“It’s always disappointing to see rare instances occur that simply don’t represent what Yik Yak is all about, and guarding against misuse is something we take very seriously,” the company said in a statement. “We’ve taken significant measures so far by adding filters, pop-up warnings, reporting, and moderation within the app, and we will constantly work to enhance these measures.”

At Mary Washington, McKinsey said, problems began in November as students were talking about whether to allow fraternities and sororities on the 5,000-student campus in Fredericksburg.

At a forum, McKinsey said she made a comment linking Greek life to sexual assault, and the reaction on Yik Yak was immediate and unrelenting. Hostile comments started flowing as soon as she stopped speaking, she said.

McKinsey said a second wave of vitriol was unleashed after she wrote an op-ed in the student newspaper in January in which she discussed a recording that was made of rugby team members at a party. The recording captures them chanting a rhyme about having sex with a dead prostitute. The school eventually suspended the rugby team because of it.

“There were waves,” McKinsey said of the abuse.

Among the comments in the weeks and months that followed, McKinsey said, there was a riff on a line from “The Hunger Games” — “We burn. You burn with us.” Her movements around campus were posted, and she said someone urged students to make problems at a Feminists United meeting, so they asked police to attend.

Banks, the attorney, said a majority of the 700 comments aimed at Feminists United were name-calling or sexist, but a handful were direct threats. In one, members were threatened with rape “in the mouth,” and at another point, someone posted about killing a “bitch.”

Because Yik Yak is anonymous, the group has no idea who posted the comments. McKinsey said Feminists United members resorted to walking in groups and informing each other where they were going out of fear for their safety. “It created an increasing level of fear and anxiety,” Banks said. “They had no way to know if people who were posting messages were sitting next to them in class or walking next to them on campus.”

On multiple occasions, Banks and McKinsey said that Feminists United met with the school president and other officials about the problems. Feminists United said that Mary Washington should have blocked Yik Yak on the school’s WiFi and taken action to identify the offenders.

In March, school officials e-mailed students about Yik Yak, saying the university had “no recourse for cyberbullying” and urged them to report incidents to the social-media site. They told students to report any direct threats to the administration or campus police.

Billingsley said that the school consulted with Virginia’s attorney general but that its options were constrained when it came to limiting access to Yik Yak. They worried that blocking it might impinge on other students’ right to free speech.

“There are First Amendment concerns when you are a state institution,” Billingsley said.

On the afternoon of April 17, Mann made a brief stop at the off-campus home she shared with Vander Briel, 30, and two other students.

Mann and Vander Briel appeared to be on different trajectories. Mann was a member of the student Senate, active in the school’s gay and lesbian club, and an activist for gay rights. Vander Briel, a former rugby player, was on his third stint at Mary Washington and was involved in few campus activities.

When Mann’s other roommates arrived that afternoon, they found her bound and unconscious, police said. Detectives say they believe that plastic shopping bags were used to asphyxiate her, according to a search warrant. Police said the two did not have a personal relationship.

Vander Briel told the roommates that he assaulted her and then fled the home. He was arrested later that day and charged, according to police and a search warrant. A preliminary hearing is scheduled for May 19.

Feminists United is not the first group to take issue with Yik Yak. Elizabeth Long, an 18-year-old from Atlanta, said she started a petition asking for Yik Yak to improve community standards after students at her school posted messages while she was recovering from a suicide attempt, telling her that she should take her life.

“It really, really hurt,” Long said.

Her petition has garnered more than 78,000 signatures.

Danielle Citron, a University of Maryland law professor and the author of “Hate Crimes in Cyberspace”, said Yik Yak’s anonymity combined with geolocation can be a powerful tool in the wrong hands.

“We’ve had threats on message boards since the ’80s,” Citron said. “Yik Yak compounds fear, because you know the individual is located nearby.”