Story highlights 4 moving vehicles shot on I-10 in Phoenix in 3 days, state Department of Public Safety says

"The best we know right now it's random," DPS director Frank Milstead says

(CNN) Somebody has shot four moving vehicles on I-10 in Phoenix in the last three days, Arizona Department of Public Safety Director Frank Milstead said Monday.

"The best we know right now it's random," Milstead said, asking members of the public to call if they have information.

Two shootings occurred about 11 a.m. Saturday, one about 10:15 p.m. Saturday and one about 4:25 a.m. Monday, he said.

A 13-year-old girl suffered a cut to her right ear Saturday morning when a bullet pierced the windshield of the SUV in which she was riding, the DPS said in a press release. She was treated at the scene and didn't need hospitalization.

The other bullets hit the sides of the vehicles and a headlight.

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