Investigators say the 4-year-old's family noticed she was missing around midmorning Thursday. They found her unresponsive and hanging in the back of a closet in a bedroom of their apartment.
Neighbor Del Evano said he heard wailing coming from the apartment at about 11:30 a.m. and saw the unresponsive child on the floor near the front door.
"It's a tragedy. It's one of those, 'I wish I didn't see it.' Seriously, I wish I didn't witness anything," said Evano.
Firefighters arrived shortly after and rushed the girl to Centinela Hospital Medical Center, but she did not survive.
"It was just horribly sad to even think about. You know, she's only 4 years old. It's just not something anyone should ever have to deal with," said neighbor Tito Livas.
The Los Angeles Police Department's Abused Child Unit is investigating, but officials say the unit looks into all undetermined deaths involving children under 11 years old.
The cause of death remained undetermined Friday. An autopsy was initially scheduled for Friday but was delayed to possibly Saturday.
A neighbor said she often saw the little girl, her mother and her grandmother in the complex, and her toys were often left outside the front door. Friday morning, the toys were gone. A family friend told Eyewitness News she was going to take the mother and grandmother to a hospital because they were so distraught.