3 Teens Arrested in 'Copycat' Case After String of Arizona Freeway Shootings The teens used a slingshot and rocks.

 -- Three teenagers were arrested in Arizona for allegedly using a slingshot and rocks to attack pedestrians and cars, in an incident officials described as a "copycat" to a string of shootings along a nearby freeway.

The teenagers allegedly shot at several cars and pedestrians on Arizona State Route 24 Saturday afternoon and evening, Maricopa County Sheriff Joe Arpaio and Arizona Department of Public Safety Director Frank Milstead said at a news conference.

Among the victims was a couple whose car window shattered from the projectile. The couple noted the license plate of the suspects' car, leading to their arrests, the officials said.

Arpaio and Milstead did not identify the teens beyond saying they were all 18.

The teens' arrests come in the wake of a string of shootings on the nearby I-10 freeway. The spree began Aug. 29, when a bullet shattered the windshield of an SUV, injuring a 13-year-old girl, authorities said. Another shot hit a tour bus, putting holes through the seats.

At least 11 shootings have been reported, all along an eight-mile stretch of road, police said.

Milstead told ABC News that it's unclear whether all of the incidents are related and also unclear whether all incidents involved bullets.

Milstead classified the incidents as "domestic terrorism." He called the suspect or suspects cowards who are putting innocent lives at risk.

The Associated Press contributed to this report.