Investigators say that on July 25, 1998, after hearing that Sigreta Hernandez, the mother of his child, would turn him in for the double killing, Saenz kidnapped, raped and murdered her at his grandmother's house.
"He leaves a note indicating that his grandmother has nothing to do with the murder and that he left the scene. And from that point on he became a fugitive," Gonzales said.
Authorities believe Saenz moved up the hierarchy from local gangs to international drug trafficking, crossing the border with falsified documents.
Los Angeles County Sheriff's authorities said Monday the motive for the 2008 murder was $500,000 in cash earmarked for Saenz that authorities seized during a traffic stop involving an alleged associate of Saenz.
As a fugitive, Saenz is suspected of traveling through Mexico, Central America, Canada and the United States while trafficking in narcotics. "He was quite an affable character who masked his identity to elude authorities, Lewis said.
While he avoided capture for years, Saenz reportedly made statements that he planned to kill a police officer if they ever found him and arrested him, according to the FBI's Most Wanted Fugitive website.
During his flight from Guadalajara to California over the weekend, authorities say, Saenz bragged about his extensive travel, including to the Los Angeles neighborhood where he was first indoctrinated into a gang, and to Los Angeles Laker pro basketball games.
"We heard rumors that not only citizens were afraid of him, but also his own gang members were afraid of him," detective Chavarria said.
The arrest of Saenz involved a multiple-agency task force that includes the Mexican National Institute of Immigration, the Mexican attorney general, the FBI's legal attache in Mexico City and its sub-office in Guadalajara, Mexico, the Los Angeles County Sheriff Department and the Los Angeles Police Department.
"It was in the endless perseverance of the hunt and continued efforts over the past decade that led to his capture," said LAPD Deputy Chief Michael Moore.
At Monday's news conference, Chavarria described Saenz as a calculated cold-blooded murderer who is more intelligent than most gang members.
But it was the chilling video that put him on the FBI's Most Wanted list, the detective said.
"He always seemed to stay one step ahead of us," Chavarria said. "It looks like he really enjoys what he does, he enjoys killing people."
Saenz was scheduled to be arraigned Monday in Pomona County, California, for the 2008 slaying and the 1998 death of Hernandez. On Wednesday he will be arraigned for the two other 1998 shooting deaths, authorities said.