Prosecutors brought felony charges this week against a former Orleans Parish Sheriff’s Office deputy accused of turning a blind eye as a violent Central City gang assaulted and stabbed an inmate at Orleans Parish Prison this spring — allegations strikingly similar to a case last year involving the same gang but a different guard.

The deputy, Solomon Colley, was arrested last month on an unrelated count of impersonating an officer after authorities said he walked into the District Attorney’s Office carrying a firearm and identified himself as a deputy even though he had been fired weeks earlier.

The Sheriff’s Office declined to provide any details about Colley’s dismissal at the time, saying only that he had been terminated during his probationary period for violating “agency policies and procedures.”

Documents released this week in response to a public records request show Colley had been fired for malfeasance after admitting to Sheriff’s Office investigators that, during a shift in late May, he allowed four members of the 3NG gang — Tyrone J. Knockum, McCoy Walker, Darrius L. Knox and Lonnie Ingram Jr. — to enter the day room in the jail, where they attacked inmate Corey Robinson.

An inter-office memorandum obtained by The New Orleans Advocate said Robinson was stabbed at least four times in the neck, back and head and taken to the hospital. The memo, written by Lt. John Morreale, said Colley had been assigned to the tier that day yet “failed to make any log book entries or security checks three hours prior to this incident.”

Morreale added, “Recruit Colley also did not document the actual stabbing which occurred on the dorm that day.”

Robinson, the injured inmate, blamed Colley for “allowing (the stabbing) to happen,” according to the memo. He told investigators he had asked Colley several times before the stabbing to move him to a different part of the jail but was rebuffed.

Colley initially disavowed knowing anything about the stabbing but appears to have been confronted with evidence to the contrary. The Sheriff’s Office redacted that portion of the memorandum, citing the need to protect “investigative techniques and aids.”

Colley was not arrested upon his July 24 firing and somehow managed to retain Sheriff’s Office credentials that he presented at the District Attorney’s Office last month after arriving for a meeting with the child support enforcement division. At that meeting, an investigator asked Colley why he was carrying a gun into the building. Colley responded by showing Sheriff’s Office identification and telling the investigator he was a deputy on suspension, according to a police report.

The investigator called the Sheriff’s Office to verify Colley’s status and learned he had been fired. The Sheriff’s Office has said Colley’s credentials were taken from him upon his firing and that it’s not clear how he had a Sheriff’s Office identification card in his possession.

On Wednesday, District Attorney Leon Cannizzaro’s office charged Colley with felony counts of malfeasance in office and impersonating a peace officer. He is scheduled to be arraigned Oct. 15.

The malfeasance case bears an uncanny resemblance to the allegations against John Dupart, a former deputy indicted last year on charges that he allowed several 3NG gang members to commit a similar jailhouse stabbing in September 2014.

In that case, Knockum, Knox, Ingram and several others attacked inmate Terrence Lee and stabbed him more than a dozen times, according to authorities. Prosecutors said Dupart opened a gate inside Orleans Parish Prison that allowed the group of inmates to move from one side of their tier to another and to attack Lee, who had to be taken to the emergency room.

Twenty members of the 3NG gang, named for its stomping grounds around Third and South Galvez streets, were named in a 2013 racketeering indictment that accused the gang of dealing drugs and committing various acts of violence over the course of a decade in Central City.

Follow Jim Mustian on Twitter, @JimMustian.