Update: Apparently the killer was also a "non-violent drug offender." From the Times:
Last fall, the man suspected in the shooting, Tyrone Howard, was arrested along with 18 other members of a drug crew that had spread violence through a stretch of public housing along the East River and was ordered into a drug diversion program, which is meant to keep some drug offenders from further crowding already overcrowded jails.
In May, he stopped taking part in the program, the officials said.
“If ever there’s a candidate not to be diverted it would be this guy,” Mr. Bratton said. “He’s a poster boy for not being diverted.”
The police said Mr. Howard was believed to have been involved in the shooting of a 28-year-old man on Sept. 1 in East Harlem.