Authorities said they had initially focused on only seven of the fatal shootings, but police said Monday that they had tied Saucedo to all nine killings, including Romero's.
After an investigation, however, police said they linked Saucedo, dubbed the "serial street shooter", to the random murders of eight others between August 2015 and July 2016.
Saucedo's targets included men, women and children, many of them ambushed near their homes in a working class neighbourhood from August 2015 to July 2016.
Police said they investigated whether Saucedo might be the so-called Phoenix freeway shooter believed responsible for nearly 12 incidents, none fatal, on I-10 in 2015.
The so-called Serial Shooters randomly targeted pedestrians; Dale Hausner killed himself while in prison, and Samuel Dieteman is serving a life sentence.
Detectives produced sketches based on statements provided by witnesses and survivors and police stumped up a $75,000 reward for information which might trace him but the killer went unstopped for more than a year.
While Saucedo knew the first victim killed in August 2015, the other slayings appear to have been random, police said.
June 10, 2016: A 19-year-old man, Manuel Castro Garcia, was shot and killed outside a home around 9:30 p.m.
"Our hearts go out to the surviving families", Phoenix police chief Jeri Williams said.
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Police said the killings were unrelated to a series of 2015 freeway shootings in Phoenix that terrified drivers. Investigators allege Saucedo pulled up alongside the auto and opened fire, hitting the victims more than 30 times.
Police previously said at least seven people were killed and two others wounded over a four-month period past year.
They said there is now no known motive for the shootings. However, they said, none of the evidence between the two series matched.
- Diego Verdugo-Sanchez was shot dead on April 1, 2016 in front of his home.
Authorities realized they had a serial shooter on the loose in June after finding links in crime scene evidence from five shootings.
Lora Romero said Saucedo's arrest, while a relief, reopened the wounds of losing her father - a hard-working, generous man who loved to watch football, play softball and tell amusing stories to his kids.
Smith said she had grown frustrated as detectives kept her in the dark about the investigation.
"I'm glad they finally got hopefully the person that's responsible", Cortes said.
"I'm happy my kids are going to be able to walk outside and I won't have to fear that they're going to get shot", said Rose Pastrana, who leads a block watch group in the neighborhood.
The next shooting didn't happen until April 1, 2016, when Verdugo-Sanchez was fatally shot.