Authorities are trying to determine if the same person fired gunshots at four vehicles along a Phoenix freeway over a three-day span.

Only one person was hurt in the shootings that began Saturday along Interstate 10, and that unidentified person suffered a non-life-threatening injury, according to authorities.

"You should be concerned. We have some people or person shooting at moving vehicles on I-10," Arizona Department of Public Safety Director Frank Milstead said at a news conference. "It has not ended in tragedy, but it could."

Authorities are asking for information from anybody who saw anything unusual on the freeway around the times when the shots were fired.

"Somebody knows something," Milstead said Monday. "We're not sure if these shootings are random or related. We don't know what the intent is. It's not known at this point if it's a copycat crime."

Two vehicles were struck within a half hour around 11 a.m. Saturday on I-10 between 19th and 59th avenues, and a third vehicle was hit on I-10 near 16th Street about 10:15 p.m. Saturday, according to the DPS.

A fourth vehicle was shot at around 4:25 a.m. Monday near 14th Avenue and I-10.

All of the shootings occurred within an 8-mile stretch of the freeway, which runs through central Phoenix.

A tour bus and an SUV were two of the vehicles fired upon, but DPS is withholding other specifics so the investigation won't be jeopardized.

The bullets have hit a windshield and a headlight, and the rest have been impacts on the passenger sides of the vehicles, Milstead said.