Authorities said Monday that a pair of sex offenders suspected of raping and murdering at least four women probably wore their court-ordered GPS devices during the crimes.
Franc Cano, 27, and Steven Dean Gordon, 45, had been required to wear the devices after serving time in prison for sexually assaulting a child under the age of 14.
Police on Monday also said that they are now "confident" that there is a fifth victim -- and perhaps more -- in a string of slayings that has been tied to a pair of registered sex offenders.
The men were formally Monday charged with raping and murdering four women, all with ties to prostitution and all who vanished off the streets of Santa Ana and Anaheim.
The two men, who both served prison terms for sexually assaulting children under the age of 14, were arrested late Friday near a trash-sorting facility where the body of one of the women, Jarrae Nykkole Estepp, was found on a conveyor belt last month.
The two are also accused in the death of Kianna Rae Jackson, 20; Martha Anaya, 28; and Josephine Monique Vargas, 34. All three went missing last fall.
At an afternoon news conference, police said the break in the case came as a result of Estepp's slaying.
The string of disappearances in Santa Ana began in early October soon after Jackson, 20, arrived in the city for a court hearing on four misdemeanor charges of prostitution and loitering to commit prostitution, according to court records. Jackson had grown up in a small, rural Northern California town and moved to Las Vegas after one semester of college.
Her mother, Kathy Menzies, said Jackson stopped responding to her text messages shortly after she arrived in Santa Ana.
Nearly three weeks after Jackson disappeared, Vargas, who grew up in Santa Ana, left a family birthday party and said she was going to the store. She was not seen again.
Vargas, 34, had a rough past that at times involved drug use and prostitution, according to court records. But she was also very close to her family, especially her mother, and had been trying to improve her life. After she disappeared, her mother, Priscilla Vargas, would walk East 1st Street in Santa Ana, among the city's roughest blocks, asking the drug dealers, street workers and anyone else who might be around if they knew anything about her eldest child, whom everyone called "Giggles."
When Anaya, 28, disappeared Nov. 12, she had been planning her daughter's birthday party at a Chuck E. Cheese. She asked her boyfriend to pick up their daughter so she could work, but stopped responding to his messages later that night.
Like the other women, Anaya had a history of prostitution, according to court records. Her family worried that her past may have reduced the urgency of the official search after her disappearance.