The incident happened at 4 p.m. in the 9900 block of De Soto Avenue.
The victim was unconscious and not breathing, according to the Los Angeles Police Department.
The victim in his 40s was shot inside an apartment before walking outside and collapsing in a stairwell. He was rushed to a hospital in critical condition.
The suspect is described as a female and fled the scene in a truck.
No arrests have been made.