Saucedo was already in custody for the 2015 murder of Raul Romero, 61.
Phoenix Police Chief Jeri Williams said in a Monday afternoon news conference the investigation was conducted in cooperation with the Phoenix Police Department, the Maricopa County Sheriff's Office, the FBI and the ATF.
During the Raul Romero investigation, police swept pawn shops in Phoenix looking for a 9mm handgun used in his murder. They located a Hi-Point 9mm pistol, which was sold to a pawn shop 16 days after the shooting, ABC15 KNXV-TV reports.
Saucedo was held on $750,000 cash bail in the Romero case. He was not named a suspect in the other investigations.
The street shootings happened between March and July 2016 and resulted in seven deaths and two injuries, KNXV reports.
Phoenix Police say they are still seeking tips from the public.
The first shooting was reported on March 17, 2016 after a driver in a Nissan drove past two teenagers and shot a 16-year-old boy in the arm, abdomen and hip. The teen survived the shooting.
The most recent incident happened on July 11, 2016. According to authorities, a 21-year-old man and his 4-year-old nephew were shot at while sitting in a vehicle. The suspect was driving an early 1990s black BMW sedan. Neither of the victims was injured.