Franklin was reportedly a mechanic for a Los Angeles Police Department station near the epicenter of the murder spree in the 1980s.
Though Harris counted Franklin as a friend, she said the news was frightening.
"It frightens me to know that somebody like that was that close," Harris said. "I don't want to believe it's true, [but] if he did what he's been accused of, God judged him for that."
Franklin has a criminal history dating back to 1989, according to records. His four previous convictions include charges of a misdemeanor battery and assault, as well as two charges for stolen property -- one of which he served jail time for.
With these latest charges, he could face the death penalty or life in prison without possibility of parole. He's expected to be arraigned today.
A handful of detectives, headed by Detective Dennis Kilcoyne, have been working full-time on the case for years, determined to find the "Grim Sleeper."
Eleven people have died so far, and there was one confirmed attempt and near killing, in the same South Los Angeles neighborhood.
"We have 12 individuals, starting in 1985. Our third victim, Thomas Steele, was the only male involved in this," said Kilcoyne.
All the slayings have been connected to the same 25-caliber handgun, and matched to the same DNA, usually saliva taken from the victims' breasts.
"The commonality is that they're all from the same general area of the city in south Los Angeles," Kilcoyne said. "I don't think I would label them all as prostitutes per se, but they certainly have troubled lifestyles. They're broken people and easy targets."
In February, LAPD offered a $500,000 reward -- the city's biggest ever -- advertised on billboards near where the victims were found. Investigators also released a 20-year-old 911 call in which a witness says he saw a van pull up in a dark alley and dump a body, which was identified as Barbara Ware.
The caller tells the dispatcher several details, everything from the license plate number of the van -- which was a dead-end lead -- to the way the body was discarded. But he refused to tell the 911 operator his name, saying he didn't see the killer.
Police say they wouldn't have known there was a serial killer on the loose if he hadn't starting killing again.
"We became aware of it right around April of 2007," LAPD Detective Bill Fallon told "Nightline" in March 2009. "And we realized there was a serial killer because of DNA hits we started getting. So when we get those hits, we're like, 'whoa.' That's when we started digging it."
But the police didn't notify the community until Christine Pelisek, a reporter from LA Weekly, began investigating.
"I was the one who told some of the family members that their daughters were victims of a serial killer," Pelisek said. "I mean, they didn't even know. The public safety committee, they had no idea. I mean, the police commission, I spoke to the police commission [to whom the police chief reports]. They didn't even know. So there were a lot of people very upset that the police didn't let the community know."
Fallon says investigators didn't want to alert the killer that they were searching for him.
"We wanted to get a a step ahead of the killer himself," he said. "I don't want you to know I'm coming for you until I find out who you are, where you are and what you are doing."