Police took the man into custody Friday night, CNN reported on Saturday.
His weapon has been connected to shootings that occurred on August 29 and August 31 on Interstate 10, said Col. Frank Milstead, director of the Arizona Department of Public Safety.
Milstead declined to provide additional details, saying the investigation is in preliminary stages. It's unclear whether the suspect is connected to the other shootings.
Phoenix residents were on edge over the random gunfire in and around I-10 between August 29 and September 10. In addition to the shootings, authorities said there were "numerous reports" of damaged cars.
The first round of gunfire late last month hit an SUV, an empty tour bus and a passenger car. More shootings followed in subsequent days, with the latest one reported last week.
'We got him!'
While state officials expressed relief at the arrest, they said the investigation is ongoing.
"We got him!," Arizona Gov. Doug Ducey tweeted after the arrest.
He urged residents to stay alert and call authorities if they have any information related to the shootings.
Copycats
The spate of shootings in Phoenix spawned copycats on roadways elsewhere in the city -- presumably by someone trying to emulate the downtown incidents.
State officials described the incidents as "domestic terrorism" and offered a $20,000 reward for information leading to an arrest.
No deaths reported
There have been no fatalities linked to the shootings. One girl, 13, was wounded when a bullet pierced the windshield of the SUV she was in -- the only injury linked to the highway shootings.
In a case described as unrelated to the shootings, police arrested three people for allegedly firing rocks with a slingshot at pedestrians and cars.