PHOENIX, Sept. 9 (UPI) -- Arizona state police are investigating nine possible shootings targeting motorists along Interstate 10 in Phoenix as domestic terrorism.
At least one person, a 13-year-old girl, has been injured in the shootings, which started Aug. 29. All of them have happened along an eight-mile stretch of the busy highway. The FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives were also investigating.
Officials have not confirmed all of the incidents were a result of gunfire, using the term "projectiles" instead of bullets to describe what struck the vehicles. It is unclear if the incidents are the work of a single person.
"It's just a matter of time, if this continues, that we have tragedy on our roadways," Public Safety Director Frank Milstead said.
"Anytime that you have multiple shootings against American citizens on a highway, that's terrorism. They're trying to frighten or kill somebody," he said.
On Aug. 29, a bullet shattered the window of an SUV on I-10, injuring a 13-year-old passenger. Another shot hit a tour bus, narrowly missing the driver, Robert McDonald. Other vehicles damaged in separate incidents include a work truck and a car driven by a Phoenix police sergeant.
Authorities announced a reward of $20,000 leading to information to the arrest and conviction of the shooter.
"If you drive that stretch of roadway, be hypervigilant," Milstead said. "Do not be distracted while you're operating your car or truck."