Debbie Kawam, as she was known in high school, was a cheerleader and a sunny presence. As the decades went on, she fell into an abyss.

The Brooklyn district attorney said the police were trying to retrace the woman’s steps to find a clear picture of her face. The man accused of killing her has been indicted on a first-degree murder charge.

The police said a man was taken into custody. The victim had been seated in a subway car at the Coney Island-Stillwell Avenue station on Sunday morning when a man set her on fire.