The victim, Islan Nettles, 21, was declared brain-dead from her injuries on Thursday and was later taken off life support at Harlem Hospital Center. She had been under the care of doctors since the attack early last Saturday, hospital officials said.

A spokeswoman for the New York City medical examiner's office, Ellen Borakove, said on Friday that the death had been ruled a homicide and the cause was "blunt force trauma."

Ms. Nettles, who, according to her LinkedIn page, was an intern assistant designer at Ay'Medici, a Harlem fashion company, was walking with a group of transgender friends on Frederick Douglass Boulevard between 147th and 148th Streets when they encountered several men across the street from the station house of Police Service Area 6, which patrols public housing developments in the area.

When the men concluded Ms. Nettles and her friends were transgender, a scuffle broke out, the police said, with punches thrown and homophobic slurs shouted.

A 20-year-old Harlem man, Paris Wilson, was arrested late Saturday and, according to a criminal complaint, was charged in the case by the Manhattan district attorney's office with misdemeanor assault and harassment. At the time of the arrest, police officers did not realize that the confrontation might have involved bias. At some point later, prosecutors said, a witness went into the Area 6 station house and told the police that homophobic language had been used.

The Police Department's hate crimes task force is now investigating the case.

Prosecutors also said that more, and graver, charges could be filed against Mr. Wilson, who on Friday remained free on bail.

On her LinkedIn page, Ms. Nettles said she had harbored ambitions to work in the fashion industry since middle school. "Fashion became a definite decision for my life after my first show with my hand designed garments in high school at the 11th grade," she wrote.

Before she worked at Ay'Medici, whose founder, Daequan Andino, did not respond to e-mails seeking comment on Friday, Ms. Nettles served as an assistant photographer and fashion instructor at the Harlem Children's Zone. She also took classes at the New York College of Technology and attended the Bread and Roses Integrated Arts High School in Harlem.

The neighborhood where Ms. Nettles was attacked has a small but growing lesbian, gay, bisexual and transgender community, said Dayan Jenniffer, the owner of the Nutrive Fitness Studio and Juice Bar on Frederick Douglass Boulevard.

Ms. Jenniffer said she had a number of transgender clients who bought her juices and health drinks "because of the hormones that they take."

Ms. Nettles was "a very cheerful, happy person," Ms. Jenniffer said, adding that the neighborhood was in shock over her death, which was first reported by the Web site DNAinfo. "It made us all a little shaken," she said. "The community here is strong, but being transgendered can be dangerous. There's still intolerance. There's still a stigma around it."

Several politicians, including the City Council speaker, Christine C. Quinn, and the public advocate, Bill de Blasio, who are both running for mayor, issued statements condemning the attack.

State Senator Daniel L. Squadron, the Senate sponsor of a bill called the Gender Expression Non-Discrimination Act, or Genda, said in a statement on Friday: "Islan was 21 years old — 21 years old. And her life and future were stolen from her. Let's be clear: intolerance, discrimination and hate have no place in New York or anywhere. Each outrage is another call: It's time for New York to send that message loudly and clearly by finally passing Genda."

Joseph Goldstein contributed reporting.