US COPS say a 16-year-old murder victim’s chilling last words may have pinpointed her ex-boyfriend as the killer.

Elena Moore was yelling and screaming the ex’s name after being stabbed in the chest at her home in Pico Rivera in Los Angeles.

3 Cops have identified Rory Murga as a 'person of interest' they want to question in connection with the murder Credit: AP:Associated Press

3 The girl's screams woke her mother at the family's LA home Credit: AP:Associated Press

LA County Sheriff deputies say the girl’s screams awoke her mother who could only watch as her daughter died.

“She was yelling and screaming his name. It's horrible,” said Lt. Eddie Hernandez.

“Can you imagine waking up to the screams of your daughter at 3:15 in the morning and this happens? It's unthinkable.”

Deputies said that after being stabbed, Elena screamed 'Rory' over and over.

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Homicide detectives said they had now identified 17-year-old Rory Murga as a person of interest who they wanted to question in connection with the girl’s murder.

The pair broke about two weeks ago after dating for about a year, it's been reported in the US.

Hernandez told the Associated Press a kitchen knife believed to be the murder weapon was found in the home.

Deputies don’t know if she let the killer into the home or whether the attacker broke in.

She was stabbed on the first floor and then ran upstairs to her mother’s bedroom where she died.

The LA Times reported that dozens of friends gathered Friday at a makeshift memorial down the street from the murder scene.

3 Deputies said after being stabbed, Elena screamed the name of Rory (pictured) over and over Credit: AP:Associated Press

Friends remembered Elena has a happy-go-lucky girl who liked to listen to metal music and to play video games, according to the paper.

Neighbour Jasmine Gonzalez, 20, said he often saw Elena and her boyfriend walking together in the neighbourhood.

"It was always just them two," she said, adding that her grandfather woke to the girl's screams, as well. "It's a shock to everybody."

Another neighbour, 60-year-old David Arias, saw the couple hanging out in front of his house from time to time.

"They seemed happy and lovey dovey," he said. "Always hugging and kissing."