Bronx man who fatally stabbed girlfriend at Unionport apartment in 2021 sentenced to 20 years

A Bronx man has been sentenced on Friday to 20 years in prison for fatally stabbing his girlfriend multiple times after a dispute in their 14th floor Unionport apartment in January 2021.

According to the Bronx District Attorney’s investigation, on Jan. 29, 2021 inside 1965 Lafayette Ave. — the Park Lane Apartments — 33-year-old Kelvin Diaz attacked his girlfriend Onelfy Then-Cordero, 29, with a broomstick, causing blunt force trauma to her head, which led to her death.

He then proceeded to stab Then-Cordero multiple times in the face with a steak knife. A neighbor was alerted by Then-Cordero’s screams for help, and when police arrived at the residence, they found Then-Cordero dead.

Diaz, who was still at the scene when police arrived admitted to officers that he stabbed Then-Cordero, and was soon arrested. Diaz pled guilty to first-degree manslaughter on Feb. 16, 2023, two years after the murder.

Then-Cordero had a young daughter at the time of her death, neighbors told media in 2021.

The Bronx has the highest number of domestic violence cases and deaths in New York City, and more than 9,500 domestic violence incidents occurred in the Bronx in 2021, according to the Bronx District Attorney’s Office.

According to a 2021 NYPD Domestic Violence Report, from 2015-2020, eight out of the top 15 community boards with the highest rates of intimate partner homicides citywide, were from the Bronx. Data from Bronx community boards 3 and 6 show 17 intimate partner homicides over that period, in neighborhoods that include Claremont, Crotona Park, Melrose, Morrisania, Bathgate and Belmont.

“An argument between a couple escalated to brutality and a woman is dead. The defendant has been held accountable but the victim’s loved ones will continue to suffer,” said Bronx District Attorney Darcel Clark. “We must do all we can to prevent domestic violence, which traumatizes so many people beyond just the victim.”

To contact the NYS Domestic and Sexual Violence Hotline call (800) 942-6906 or text (844) 997-2121. All conversations are confidential, secure and available 24/7 in most languages.