The shooting was reported around 8:15 a.m. at The Dylan Apartments in the 7100 block of Santa Monica Boulevard. The Los Angeles County Sheriff's SWAT team responded to the scene after the woman was sent to Cedars-Sinai hospital with gunshot wounds.
The suspected shooter was in an adjoining unit in the complex and the victim - who described only as a woman in her 50s - was shot through the wall, authorities said.
"[Patrol deputies] immediately noticed that it was that neighbor where those rounds came from, the established a containment and requested our Special Forces bureau to come out and assist," said LASD Public Information Officer Miguel Meza, who said at least five shots were fired.
Authorities said the victim was shot twice, once in the neck, but is expected to recover.
"The bullets going through the wall reduced the velocity of the bullet and decreased the deadliness of the bullet," said LACoFD Public Information Officer Craig Little.
The shooter then barricaded themselves in the unit. Sheriff's deputies unsuccessfully attempted to make contact with the suspect and was believed to have left the area. A description of the suspect was not immediately released.
At one point, loud blasts could be heard coming from the building, likely the result of deputies setting off a flash-bang in hopes of getting the suspect to surrender.
No other injuries were reported.