A 55-year-old Bronx man has been busted for fatally stabbing two people and wounding another during a fight sparked by an alleged attempted groping, cops say.

Derrick Williams was busted Wednesday night and charged with two counts of murder and a single attempted-murder rap in the Aug. 25 violence that erupted inside a building on Rochambeau Avenue in Norwood, authorities said. 

A 45-year-old man and two women, 29 and 33, were heading up a stairwell inside the building near the East 206th Street intersection around 10:20 p.m. when Williams tried to grope one of the women, police said. 

The incident led to an argument, and the trio followed Williams to an apartment on the fourth floor.

The group fought, with the suspect stabbing the women, who were still able to flee the building – leaving Williams and the other man, Roberto Jimenez, to square up, authorities said.

Police responding to a 911 call later found the younger woman, identified by cops as Gina Cooks, with a fatal stab wound to the chest, cops said. 

The other woman, 33, had been slashed in the hand, authorities said. 

Cooks was pronounced dead at St. Barnabas Hospital, while the 33-year-old was listed in stable condition.

When cops went inside the building, they found Jimenez also dead from multiple stab wounds in his torso, the NYPD said.

Both Williams and Jimenez lived in the same building where the deadly violence occurred, police said.

Cooks lived more than a mile away in Fordham Heights.