A New York woman has admitted her involvement in the fatal stabbing of her former boyfriend outside a Long Island yacht club, pleading guilty to manslaughter and hindering prosecution. Prosecutors say she drove the vehicle used during the confrontation while her then-boyfriend allegedly chased and fatally stabbed the victim after an encounter at the marina.
Guilty Plea Entered in 2025 Homicide Case
Kacy Corso, 34, pleaded guilty earlier this week to manslaughter and hindering prosecution in connection with the November 2025 killing of Christopher Millwater, 52.
Corso had originally been indicted in December 2025 alongside her then-boyfriend, Victor Panebianco, 32, on a charge of second-degree murder. Millwater was Corso’s former boyfriend.
As part of her plea agreement, Corso agreed to fully cooperate with prosecutors in their case against Panebianco. In exchange, prosecutors are expected to recommend a seven-year prison sentence. She is scheduled to be sentenced in September.
Attorney Says She Accepted Responsibility
Outside the courthouse in Riverhead, Corso’s attorney said his client accepted responsibility for her actions but maintained that her involvement in the incident was limited.
During the plea hearing, State Supreme Court Justice Timothy Mazzei asked Corso what the plan had been before the confrontation.
According to courtroom reports, Corso quietly responded that there was no plan, though she admitted that her intent had been to cause serious physical injury to her former boyfriend.
Deadly Encounter at Stony Brook Yacht Club
The fatal incident occurred during the early morning hours of Nov. 10, 2025, at the Stony Brook Yacht Club on 21 Shore Road in Suffolk County.
According to prosecutors, Corso drove into the marina parking lot, where Millwater soon arrived and parked beside her vehicle.
Investigators allege Corso then positioned her vehicle in front of Millwater’s car. Panebianco allegedly exited the passenger side of Corso’s vehicle and approached Millwater.
Authorities said Millwater attempted to drive around Corso’s vehicle toward the parking lot exit, but Corso allegedly drove her vehicle into his car, preventing him from leaving.
Victim Chased and Fatally Stabbed
After the collision, prosecutors say Millwater got out of his vehicle and ran from the scene.
Surveillance footage allegedly captured Panebianco chasing after him while carrying an object believed to be the murder weapon.
Authorities said Millwater was stabbed through the heart and lungs during the attack.
According to prosecutors, the victim cried out, “You’re stabbing me?” as he was being attacked.
Investigators further allege that after Millwater fell to the ground, Panebianco threatened to kill him and warned him to stay away from Corso.
Prosecutors also said Corso could be heard yelling at Millwater during the assault. They allege Panebianco then kicked the victim in the head before returning to Corso’s vehicle, and the pair drove away together.
Victim Died After Hospitalization
Police responded to the scene at approximately 3:40 a.m. and found Millwater suffering from multiple stab wounds.
Emergency responders transported him to Stony Brook University Hospital, where he later died from his injuries.
Facebook Interaction Mentioned During Investigation
Investigators noted that Millwater had “liked” one of Corso’s Facebook posts just days before the fatal confrontation, a detail that surfaced during reporting after the indictment.
While that social media activity became part of the timeline surrounding the case, prosecutors have focused their criminal allegations on the events that unfolded at the yacht club parking lot.
Murder Case Against Co-Defendant Continues
Unlike Corso, Victor Panebianco has not entered a plea agreement and continues to face a charge of second-degree murder.
If convicted, he could receive a prison sentence of up to 25 years.
With Corso’s guilty plea now secured, prosecutors are expected to use her cooperation as they continue pursuing the murder case against Panebianco over the death of Christopher Millwater.
