The advertisement promoting the new "Halloween" movie is on Pico Blvd. in Mid-City.
Sabo swapped out an image of the movie's serial killer, Michael Myers, and replaced it with one of Waters.
The image shows Waters holding a butcher knife in her right hand, looking ready to attack.
The phrase "#Uncivil Democrats" is also added.
Waters represents California's 43rd District in Congress.
Correction: An earlier version of this story stated the billboard was located in West Hollywood but has since been corrected to Mid-City.