In February, after serving almost 13 years in prison, a Brooklyn man named John Giuca had his murder conviction thrown out by an appellate court citing violations by the prosecutor—a former darling of the Brooklyn DA’s Homicide Bureau who now has her own true-crime TV show.

The court ordered a retrial but instead of letting Giuca out on bail, the trial judge sent him to Rikers, giving the DA time to ponder its next move without the political black eye of having let him go free. So far, prosecutors have filed papers seeking permission to appeal the appellate court’s decision.

Now, The Daily Beast has obtained a full and detailed confession given less than two weeks ago to detectives from the other man convicted of the crime. That man, Antonio Russo, who has never spoken to the press, did not implicate Giuca in any way in his account of what happened in October of 2003 to Mark Fisher, a college student from New Jersey gunned down on a quiet residential street in Brooklyn after attending a party at Giuca’s home.

Fisher was shot five times and his body—along with two shell casings—was found in the early morning at the foot of a driveway on Argyle Road in the Ditmas Park section of Brooklyn, several blocks from Giuca’s house and across the street from the house of another party-goer, Albert Cleary. When interviewed that morning by police, many residents of the block reported hearing multiple gunshots and the sounds of a car door opening and closing, and a car driving away. One couple heard the sound of young people’s’ voices, including what they believed was a distinct female voice. (Giuca’s defense team has suggested that the young woman plausibly could have been Angel DiPietro, who also attended and left the party with Cleary and—incredibly—is now a prosecutor in the Brooklyn DA’s office; she changed her story several times during the initial investigation and again under oath at trial and, in 2007, was sued unsuccessfully by Mark Fisher’s parents for her role in the events leading to their son’s death.)

Ultimately, both Russo—who had also attended the party—and Giuca were arrested and charged with the murder, which the DA argued at his trial was, alternatively: part of a gang initiation “ordered” by Giuca; retaliation for Fisher’s having “disrespected” Giuca’s home by sitting on a coffee table; or the result of a robbery gone wrong. Russo was charged with the actual shooting while Giuca was indicted for supplying Russo with the gun that night so he could rob or kill Mark Fisher. Both men pleaded innocent and in 2005, after separate trials that ended in guilty verdicts, were both sentenced to 25 years to life.

Over the years, Giuca filed several failed appeals and, in 2014, made an unsuccessful bid to get the Brooklyn DA’s highly touted Conviction Review Unit to vacate the conviction. (In addition to prosecutorial misconduct, Giuca’s defense team developed piles of evidence documenting inconsistent witness statements and obtained three sworn witness recantations, none of which was credited by the DA. It is unclear whether the DA’s investigators interviewed Russo during their review.) Then, early this year, Giuca’s conviction was tossed in a unanimous decision by an appellate panel, which found that the prosecutor, Anna Sigga-Nicolazzi, had withheld information favorable to Giuca and failed to correct knowingly false or misleading witness testimony.

On March 22nd, the DA sent detectives upstate to interview Russo in prison. In that meeting, according to a police report known as a DD5, Russo confessed to killing Mark Fisher (the DD5 was sent by the prosecutor to Giuca’s attorney and the judge, and was characterized by the prosecutor as “potential Brady ,” or exculpatory, material). Russo told detectives that he shot Fisher after he and Fisher left Giuca’s home and were walking several blocks away on Argyle Road. Russo also said that the “gun was his” and that he “had it for awhile and shot someone else with it.” The DD5, which summarizes Russo’s comments but does not include the detectives’ questions, also notes that “he could not say where he got [the gun] nor how long he owned it.”

Russo described what amounts to an execution. He told the detectives that he took the gun out of his waistband, pointed it at Fisher, took Fisher’s wallet and “told Fisher to run,” after which he “fired one shot into the ground to let Fisher know it was a real gun.” The DD5 goes on to note that “Fisher said why did you shoot me and Russo fired the rest of the bullets from the gun at Fisher, killing him.”

Asked about the interview, a spokesperson for the DA’s office said that “we don’t comment on pending cases,” referring to the fact that the office is currently appealing the vacated conviction.

Nothing in the DD5 indicates that Russo was acting on anyone else’s behalf when he decided to rob and then shoot Fisher.

Witness statements taken by police during the initial murder investigation include information that Russo had previously threatened people, engaged in violent behavior and carried a gun in his waistband.

In his recent prison interview, Russo claimed that he was seen by a “young woman in a car” who looked at him “and could identify him” before he “ran back towards his house,” disposing of Fisher’s wallet in a nearby sewer. While Fisher’s wallet was in fact recovered from a sewer near Russo’s apartment building, there are several elements of his confession that are contradicted by the evidence. Specifically, according to the DD5, Russo told the detectives he shot Fisher with a 9mm German Luger, firing all 16 shots in the magazine. In fact, the gun used to kill Mark Fisher was a .22 caliber; none of the residents of Argyle Road reported hearing anywhere near 16 shots. It is unclear whether detectives pressed Russo on these discrepancies.

It is also unclear from the DD5 whether the detectives questioned Russo directly about whether Giuca had anything at all to do with orchestrating the robbery of Fisher, or his murder. If they did not—and there is nothing in the interview document that shows that they did—it is an omission that suggests they may have been more interested in trying to find a witness to retry Giuca, waiting in Rikers, and regain the “win” the appeals court took from them, than in finding out what in fact happened to Mark Fisher.

After all, that’s what Russo, with nothing to gain by finally confessing to the crime, seems to have told them.