Aaron Saucedo, initially arrested on April 19 for a fatal shooting in 2015, was re-booked on Monday into a Maricopa county jail and is now facing 26 charges for a total of 12 shootings, reports USA Today.
The suspect has now been held responsible for the deaths of eight other people, whom he killed between January and July 2016 in a predominantly Latino neighbourhood of Phoenix.
Police said they investigated whether Saucedo might be the so-called Phoenix freeway shooter, believed responsible for nearly 12 incidents, none of them fatal, on Interstate 10 in 2015.
"To bring this killer to justice and get it right", Stanton said.
The Phoenix police chief and mayor appeared alongside other top officials including the county's top prosecutor to announce the break in a case that had appeared largely stalled in recent months as leads and tips dried up.
While Saucedo knew the first victim killed in August 2015, the other slayings appear to have been random, police said. He killed Manny Castro Garcia on June 10, 2016.
During his initial court appearance, the judge read a long list of charges, including eight counts of first-degree murder, six counts of drive-by shooting, three counts of attempted murder and one count of aggravated assault, after which Saucedo exclaimed, "I'm innocent".
"Our hearts go out to the surviving families", Phoenix police chief Jeri Williams said.
Saucedo was a bus driver for the city of Phoenix through a temp agency for several months in 2015, Phoenix police said.
Saucedo told authorities he had changed his appearance and stopped driving his BMW after the police released descriptions of him and the auto last summer, Howard said.
Investigators initially believed a serial shooter was responsible for seven deaths a year ago, but in recent weeks they determined two other victims - the one killed in August 2015 and another person slain in January 2016 - were shot by the so-called "serial street shooter" who they believe to be Saucedo.
April 1: Diego Verdugo-Sanchez, 21, killed at around 9:00 p.m.
They said there is now no known motive for the shootings.
"I had a gut feeling it was him", she told the Republic.
They found a gun that he had pawned in September 2015 and matched it to evidence from the murder of Romero, 61, who was gunned down outside his home but had not been included in the pattern identified by police.
She said she had grown frustrated about being kept in the dark about the investigation.
The next shooting did not happen until April 1 2016, when Mr Verdugo-Sanchez was fatally shot.
"When they showed me the picture, I did get a little chills", he said.
The shootings stymied the authorities for months, and the police are still unsure of Saucedo's motive.