The girl's screams woke her mother up and roused neighbors from sleep just after 3 am in the quiet neighborhood in Pico Rivera, about 10 miles southeast of downtown Los Angeles.
Elena Lillian Moore had been stabbed at least once in the chest, and she collapsed and died in front of her mother a short time after yelling the name 'Rory.'
'She was yelling and screaming his name. It's horrible,' Hernandez said. 'Can you imagine waking up to the screams of your daughter at 3:15 in the morning and this happens? It's unthinkable.'
Investigators are now searching for Elena's 17-year-old former boyfriend, Rory Murga. Evidence found at the crime scene also tied Rory to the home, Hernandez said.
Two photographs of Rory were released after investigators searched for him for twelve hours.
A kitchen knife believed to be the weapon used in the attack was recovered inside the home.
It was unclear whether Elena let her killer into the home or whether the attacker broke in, he said, adding that damage found to the back door could have happened in the past.
The stabbing happened downstairs, and Elena was able to run upstairs to her mother before collapsing.
Elena, also was known as Lily, and Rory dated for a year until she ended the relationship two weeks ago, he said.