Williams announced Saucedo has been linked to eight other shootings, bringing to nine the total number of killings investigators linked to him.
"They had a clear mission: bring this killer to justice and get it right".
Sylvia Ellis, the mother and grandmother of two victims, said she was reeling from news of the charges after the trail seemed to have grown cold for so long.
One tipster could receive a $75,000 reward for information leading to the arrest, police said.
Police say it appears Saucedo didn't know any of the victims except for his mother's boyfriend, Raul Romero, who was found shot to death in his driveway.
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The gunman's targets included men, women and children, many of them ambushed near their homes in a working-class neighborhood from August 2015 to July 2016.
Investigators initially believed a serial shooter was responsible for seven deaths previous year, but in recent weeks they determined two other victims were also shot by the same gunman, who they believe to be Saucedo, including the victim killed in August 2015. She said he was never a trouble-maker and preferred playing basketball with friends over partying. Police have since linked this murder to the string of street shootings.
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Police arrested Saucedo last in connection with a separate 2015 killing.
"The fact of them finding somebody, at least it was some type of news", Smith said.
Saucedo was being held on first-degree murder charges in Romero's death when police announced new charges in the serial street shootings case.
This undated photo provided by the Maricopa County Sheriff's Office shows Aaron Saucedo. But they said in a statement the evidence includes surveillance video, witness statements and ballistics material. The shootings ended abruptly in July amid a massive publicity effort, and Howard said Saucedo told investigators that he had changed his appearance and stopped driving his BMW around that time.
The next shooting didn't happen until April 1, 2016, when Verdugo-Sanchez was fatally shot.
Manuel Castro Garcia, 19, was murdered outside his home on June 10, 2016.
Shots were fired into a auto on July 11, 2016; a man and a 4-year-old boy inside escaped unhurt.