Students, family and friends gather at a memorial service for Grace Mann in Fredericksburg, Va., on Friday. (Reza A. Marvashti for The Washington Post)

Going between an event highlighting the bullying of gays and a political rally, Grace Rebecca Mann popped into the Fredericksburg, Va., home she shared with three other University of Mary Washington students, her father and friends said.

The stop on April 17 was supposed to be brief for the 20-year-old, who was one of the school's most prominent students and a leading voice for feminist and gay causes. But she would never leave.

Two roommates would find her a short time later, unconscious and bound, according to a search warrant. A third roommate was later charged in her death, a killing that remains a mystery to her McLean family and the campus.

Hundreds turned out for a memorial service Friday, where she was remembered as a “force of nature” and a message from feminist icon Gloria Steinem was shared.

This week, in the Mann family’s first interview, the student’s father, Judge Thomas P. Mann of Fairfax County Juvenile and Domestic Relations Court, said authorities have not told the family of a motive in his daughter’s killing, but he said it cut short a life full of promise. The junior served in the Student Senate, was a board member of the group Feminists United, an appointee to the school’s task force on sexual assault and a member of the gay men and lesbians’ club, among other activities. Friends said she was openly gay.

Grace Rebecca Mann (Courtesy of the Mann family)

“She just wanted the world to be a beautiful place, a safe place and a kind place,” Mann said.

Steven Vander Briel, 30, who is accused in Mann’s slaying, was in his third stint at Mary Washington. Friends said he was a political science major involved in few activities around campus. He was described as mellow, laid back and friendly — so much so that he earned the nickname “Care Bear” during his first four years at the school, from 2002 to 2006. They also said that the New Jersey native played rugby for the school’s club team during that period and is into music.

Micaela Butler, a friend of Mann’s and an acquaintance of Vander Briel’s, said she and other friends are baffled by the slaying. She said she knew of no tension between Mann and Vander Briel.

“In hindsight, you can usually say, ‘Something was off,’ ” Butler said. “He was fine.”

Vander Briel’s family and an attorney did not return calls for comment.

Mann’s father and friends described her as untroubled — even happy — the day of her death. She was preparing for finals and had a schedule full of political activities, which was normal for her. Cedric B. Rucker, the school’s dean of student life, said he bumped into Mann on campus just hours before she was killed. He described her as “bubbly.”

“She gave me a hug and then launched into a conversation,” Rucker said. “It was so typically Grace.”

Grace Mann's parents, Thomas and Melissa Mann, listen to friends recall memories of their daughter’s life Friday on the campus of the University of Mary Washington. (Reza A. Marvashti / For the Washington Post)

Friends said Mann was participating in a “Day of Silence” to call attention to the bullying of gay men and lesbians. She headed home in the afternoon to the red brick home, on a suburban street, that she shared with Vander Briel and two women.

Vander Briel had again enrolled at Mary Washington for the spring semester after spending time in the Seattle area, where he worked for a digital marketing company. A representative for that company said that Vander Briel always went the “extra mile” to help people, both professionally and personally. The representative said that before Vander Briel left in September 2014, he told him he was going to go back east to pursue a music career.

Vander Briel initially left Mary Washington in 2006, returned for 2007 and 2008, and then left again, according to the school. Friends said they didn’t know why he dropped out twice. Vander Briel was just two classes shy of graduating and was on track to get his degree this spring. Fredericksburg police said that Mann and Vander Briel did not have a personal relationship. Mann’s father said that Vander Briel was simply renting a room in the house.

Police were called to the house about 3 p.m. April 17, according to a news release. Mann’s two female roommates had come home to find her unconscious and bound. Police believe that plastic shopping bags were used to asphyxiate her, according to a search warrant. Vander Briel allegedly told the roommates that he had assaulted Mann and then fled. The roommates performed CPR on her and she was taken to the hospital, where she died. Both of those roommates declined to comment.

Vander Briel was captured later that day after a search by officers and a bloodhound. He was charged with first-degree murder and abduction and is being held without bond. A preliminary hearing is scheduled for May 19.

Detectives recovered two belts and a roll of duct tape from the home Mann rented, according to a search warrant.

An outpouring of grief has followed Mann’s death. Her funeral, at Temple Rodef Shalom in Falls Church on Tuesday, drew hundreds of mourners, and Friday’s memorial drew hundreds more to the Mary Washington campus.

Paige McKinsey, president of Feminists United at Mary Washington, recalled Mann telling her during a march against sexual assault that Mann needed to lead it “because I’m the loudest.” A roommate remembered how Mann would plaster an “I am a Feminist” sticker on people entering the house — and they would get two stickers if they did not like it. A message from Steinem, Mann’s idol, said she was “inspired” by Mann’s work.

“She was a force of nature fueled by passion and determination,” McKinsey said. “Grace Mann wasn’t going to change the world. She did change the world.”

Afterward, to remember Mann, the mourners sent butterflies aloft.

Mann’s work with Feminists United placed her at the center of a contentious debate this year over whether to allow Greek life on campus.

Mann’s father said she hoped to become a lawyer and possibly work on human rights issues. He said she would hang around the courthouse in Fairfax, spending time with judges, attorneys and police officers, from the time she was 6 or 8. In high school, she worked in hospice care for the elderly.

Eleanor Smeal, president of the Feminist Majority Foundation, said at Friday's memorial that others would carry on the work Mann started.

“She had a short life, but an impactful life,” Smeal said.