According to new reports, it all came unraveled when the former governor fired 50-year-old Mildred Patricia Baena in an attempt to save his marriage with Maria Shriver.
ABC News identified Baena on Wednesday as Schwarzenegger's one-time mistress, adding that she was also known as Patty and she worked as a housekeeper and assistant for Schwarzenegger's family for more than 20 years at their Brentwood estate.
According to the New York Times, Baena was pregnant at the same time Shriver was also pregnant with the youngest of the couple's four children, Christopher, who is now 13 years old.
The Times also said that rumors of a secret child were rampant during Schwarzenegger's first run for governor. A former aide said Schwarzenegger was the target of several false claims while trying to unseat Gray Davis.
The aide said this week's revelations represent a time in Schwarzenegger's life when he wasn't in office.
"From his Hollywood life, I don't see this as a surprise," said former advisor Sean Walsh. "Were this to have occurred while he was governor, I would be shocked. I don't believe some of the other rumors and allegations that are floating around with regards to any activities while he was governor."
Some say Shriver may have known everything long before Monday's announcement.
"I know for a fact that she's heard the rumors about the child out of wedlock before, and they've tried different things to patch it up, but nothing has worked," said Ian Halperin, a biographer.
Initial reports by the Los Angeles Times said Baena retired from her housekeeping duties in January, but Radar Online said Wednesday that Schwarzenegger fired her to save his crumbling marriage.
The website said Baena then threatened to go public with the news of the affair and their child, which prompted Schwarzenegger to come forward with the news on his own.
Shriver has reportedly hired a divorce attorney. One family law expert says that while it's likely the couple has a pre-nuptial agreement Schwarzenegger has a financial obligation to care for his illegitimate child.
Info on ex-gov.'s mistress comes to light
Currently, little is known about the former governor's illegitimate son, who is believed to be 13 or 14 years old.
"Within hours, days and weeks, we will know everything we want to know of the mother of the child," said ABC News consultant Howard Bragman.
According to court records, Baena has been married at least twice.
Baena was married at the time of the affair but filed for divorce from her husband, Rogelio Baena, in 2008. According to legal documents obtained by Eyewitness News, the couple's divorce is still pending. The couple legally separated in 1997, 21 days after the birth of the baby fathered by Schwarzenegger.
There is another indicator that the baby's birth stirred conflict in Baena's marriage. On the son's birth certificate, Rogelio Baena is listed as the father. Yet in the divorce papers, the couple says they have no minor children together.
Baena, the boy and her other children live in an upscale neighborhood in Bakersfield. The news of the scandal was a shock to neighbors. One neighbor, Marty Steelman, said Baena moved into her four-bedroom home about one year ago with her teenage son and another man.
Steelman said she knew Baena worked for Schwarzenegger but never talked to her about it. Steelman also said Baena did not live at her Bakersfield home full time until just about two months ago. Before that, Baena reportedly spent her weekdays working in Calabasas.
Steelman described Baena's teenage son as being very polite and intelligent.
"This young man is just at the top in being polite and very cordial, someone you want to be around," Steelman said. "He's a very highly-intelligent young man."
Steelman said she and her husband last saw Baena, her son and another other man at their home Sunday evening.
Baena's adult children live in a condominium in Van Nuys. According to neighbor Norma Foster, Baena regularly visited and picked up her grandchildren for school.
Foster said Baena's youngest son strongly resembles his celebrity father, adding that Baena is polite and always says hello.
Maria Shriver makes 'Oprah' appearance
Shriver appeared Tuesday on stage in Chicago with Oprah Winfrey as part of the final series of tapings for "The Oprah Winfrey Show." Shriver received a loud ovation from the thousands of audience members. She did not mention Schwarzenegger during the event.
Shriver said Winfrey has "Given me love, support, wisdom, and most of all, the truth."
People who live and work near Schwarzenegger's Santa Monica office say they feel for his entire family, especially Shriver.
"I don't know how she can do anything other than walk away with her head held high, because she's certainly never lived her life with anything other than very high morals. A lot of class, she's a very classy lady," said Santa Monica resident Kim Hightower.