A lovers' quarrel turned deadly when a Bronx woman stabbed her boyfriend in the chest on East 188th Street Sunday, according to police.

Police have accused 21-year-old Laura Montanez of piercing Kedwin Valerio's heart with a knife around 6:30 p.m. inside his mother's apartment at 311 East 188th St.

Police said the two were arguing over a Facebook password, and Valerio started throwing things at Montanez. Then she grabbed the knife. 

Valerio was pronounced dead at St. Barnabas Hospital.

Montanez's mother spoke with News 12 outside the apartment building and claimed that Valerio was abusive toward her daughter. She said Montanez was defending herself.

She said her daughter was the one who called 911 about the incident, a claim Valerio's family disputed.

Valerio's brother told News 12 that the victim was more likely to have secluded himself by listening to music or going on a run than get involved in an argument. He accused Montanez of acting out of jealousy.

Police said they took Montanez into custody at the scene and charged her with murder, manslaughter and criminal possession of a weapon.