Edith Moreno, 12, and her older sister Diana Moreno, 17, were found dead around 11:40 a.m. Wednesday at a home in the 7800 block of Irvine Avenue in North Hollywood.
Police say one of the victims was found in the front room inside the main house and the other was found in a converted garage in the back.
According to police the sisters throats were cut. Gomez, who was found at the location with knife wounds to her upper body and wrists, was taken to a hospital, where she underwent surgery and was listed in serious condition, police said.
The girls also have a 14-year-old sibling who was not at the crime scene, but has been accounted for, police said.
Neighbor Phillip Ponce says it is hard to believe that this happened.
"It was shocking to everybody. It's a quiet neighborhood. It was surprising I didn't hear anything because I was home all day," said Ponce. "Then the cops showed up. One of the guys who used to live in the front, his buddy showed up and I guess they were going to hang out or something. He saw the bodies and called the cops."
Gomez was booked Friday for double homicide and is being held in lieu of $2 million bail.
CNS contributed to this story.