Christopher Buggs, 26, was awaiting trial in a 2018 murder when he was released on an unrelated case.
In the unrelated case, he was sentenced to 30 days of time served for criminal contempt.
He's accused of killing 55-year-old Ernest Brownlee outside a bodega in Bedford-Stuyvesant.
Brownlee was apparently a career criminal who killed two men in the 1980s.
The Correction Department says it is conducting a full investigation into how Buggs was released.
"A full investigation into how this happened is underway," Deputy Commissioner of Public Information Peter Thorne said. "Right now, we are working with our law enforcement partners to return this individual to custody."
Four correction officers have since been suspended in connection to the mistaken release, including Assistant Deputy Warden Kevin Roulston, the tour commander, who gave the final signoff for the release.
Two correction officers and a captain were also suspended.
"This is being fully investigated right now," Mayor Bill de Blasio said. "We are going to put additional safeguards in place to make sure this never happens again. It's very frustrating. It was based on a court order, but it was apparently one case that this inmate had connected to him, but there were other charges obviously as well that should have meant he remained incarcerated. So we are going to get a full review of this immediately, make whatever changes we have to. In the meantime, we have a high level of confidence that he will be re-apprehended shortly."
Anyone with information in regard to the whereabouts of this individual is asked to call the NYPD's Crime Stoppers Hotline at 1-800-577-TIPS (8477) or for Spanish, 1-888-57-PISTA (74782).
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