Sarah Paulson is once again joining the Ryan Murphy Cinematic Universe.The veteran actor is currently starring in Murphy's All's Fair on Hulu, was recently announced as part of the star-studded cast of American Horror Story Season 13, and is now joining the cast of the upcoming fourth season of Monster.Monster Season 4 will focus on Lizzie Borden, but will also apparently explore the lives of other female killers. Paulson will be playing serial killer Aileen Wuornos in the show. But who was Wuornos? Here's everything you need to know.Who is Aileen Wuornos?Aileen Carol Wuornos was born on February 9, 1956, in Rochester, Michigan. She had a difficult childhood, with her father being convicted of child molestation and killing himself in prison when she was young. Her mother then left Wuornos and her brother in the care of her grandparents, who were also allegedly abusive.At the age of 14, she gave birth to a son and gave the child up for adoption. She was kicked out of her home shortly after.In her later teen years and twenties, Wuornos lived as a drifter, working as a sex worker, and was arrested for numerous petty crimes, including assault and shoplifting. Throughout the 1980s, she continued working as a sex worker until she started committing murders in 1989.How many people did Aileen Wuornos murder?From 1989 to 1990, Wuornos murdered seven middle-aged white men. Their names were Richard Mallory, David Spears, Charles Carskaddon, Troy Burress, Charles "Dick" Humphreys, Peter Siems, and Walter Antonio. In 1991, Wuornos was arrested and confessed to several of the murders, saying it was self-defense after the men attempted to rape her.In 1992, she faced a trial for the murder of Mallory. She was found guilty on all counts and sentenced to death. Later that year, she pleaded no contest to the murders of Humphreys, Burress, and Spears, and eventually pleaded guilty to the murder of Carskaddon and Antonio. As Siems's body was never found, she was not charged with his murder.In total, she was sentenced to six death sentences.Wuornos was executed in 2002.Was Aileen Wuornos a lesbian?While Aileen Wuornos' sex work clients were men, she had relationships with women in her personal life.In 1986, Wuornos met Tyria Moore at a gay bar called Zodiac in Daytona Beach, Florida, and soon, the two formed a relationship. They dated until shortly before Wuornos was arrested in 1992.After Wuornos was arrested, police had Moore help convince her to confess. When Wuornos called Moore from prison, Moore said that the police were "coming after me" and urged Wuornos to confess."I'm not gonna let you go to jail. Ty, I love you. If I have to confess everything just to keep you from getting in trouble, I will," Wuornos said in the phone call, which was recorded.What actors have played Aileen Wuornos?Charlize Theron famously played Aileen Wuornos in the 2003 film Monster, opposite Christina Ricci as Moore. She was awarded the Academy Award for Best Actress for her role. Lily Rabe played Wuornos in the fifth season of American Horror Story, titled Hotel. In her episode, a group of ghosts of serial killers, including Wuornos, Richard Ramirez, John Wayne Gacy, and Jeffrey Dahmer, meet in the hotel on Halloween night.Peyton List played Wuonros in the 2021 film Aileen Wuornos: American Boogeywoman, and Hacks star Jean Smart played Wuornos in the 1992 film Overkill: The Aileen Wuornos Story.Why is Sarah Paulson playing Aileen Wuornos?Sarah Paulson is set to play Wuornos in the upcoming fourth season of Ryan Murphy's true-crime series Monster, according to Variety. The fourth season will focus on Lizzie Borden, played by Ella Beatty. Monster Season 3 star Charlie Hunnam will also star, along with Rebecca Hall, Billie Lourd, Jessica Barden, and Vicky Krieps.