Police say the officer shot her ex-girlfriend and another woman - allegedly her ex's new girlfriend.
Sources tell CBS2 the officer's ex-girlfriend lives in the home where the shooting took place. The couple reportedly ended their relationship about a month ago but kept in touch.
It happened on 19th Avenue and 79th Street in Bensonhurst. Multiple 911 calls were made in the area as gunfire rang out.
As CBS2's Cory James reports, sources identify the off-duty officer as 31-year-old Yvonne Wu and say she showed up to her 23-year-old ex-girlfriend's home Wednesday.
Around 5 p.m., Wu's ex returned home with a woman who has been identified as 24-year-old Jamie Liang.
At some point after they arrived, police say the five-and-a-half-year NYPD veteran admitted to firing her gun.
"One female, a 24-year-old, was found lying in the living room area, and the second female, a 23-year-old, was found lying on the floor in the bedroom," NYPD Brooklyn South Assistant Chief Michael Kemper said.
Police are trying to determine if Wu was trespassing or waiting for the women to arrive, CBS2's John Dias reported.
"We believe all three parties knew each other," Kemper said.
Valerie Wares says she saw police do CPR on one of the women and watched the other go into the back of the ambulance.
Liang later died at the hospital. Police say she was shot at least once in the chest.
What shocked Wares the most was learning the person she witnessed getting placed into the back of a patrol car is someone who was given a badge to protect and serve.
Police say when they arrived, Wu was outside the home and confessed to the shooting.
"In her NYPD jacket, which was curious," Wares said. "It was so strange. She was so peaceful and calm."
Police say it's not clear whether she used her service weapon.
"She last worked last night ... She got off this morning, and she was scheduled to go back tonight," Kemper said.
We don't know how the officer got into the home and how long she was waiting inside.
Police say the ex-girlfriend was shot in the torso and is expected to be OK.
Charges against Wu are pending.
CBS2's John Dias contributed to this report. Editor's note: This story was first published Oct. 13.
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