The transformation of Islan Nettles over the last year was something her friends and relatives discussed with barely concealed awe.

After years of often being hungry and on the verge of homelessness, Ms. Nettles, 21, had recently moved into her own apartment, found a job at an H & M clothing store and was designing her own fashion line.

Most important, she had begun to live publicly as transgender. Seemingly overnight, friends and relatives said, she had metamorphosed from a shy and insecure youth into a radiantly confident young woman.

And then she was killed.

Just after midnight on Aug. 17, a young man knocked her to the ground after learning she was transgender and struck her with his fists until she was unconscious and battered beyond recognition, according to accounts from the police and friends. She lingered in a coma for less than a week before being taken off life support.