Story highlights Four vehicles are shot in the past two days along a stretch of I-10 in Phoenix

There have been 10 recent shootings in the same area; there are no suspects

A state official says, "All of these acts are potentially lethal encounters"

(CNN) Ten shootings, 11 days, all along one small, busy stretch of Interstate-10 through downtown Phoenix.

And no suspects, and no end in sight -- yet.

Fresh off another shooting Wednesday, the head of the Arizona Department of Public Safety called ending this spree "job one" for his and partner agencies. But to do so, he said, the public may need to help.

"Somebody is very aware of who this is," Col. Frank Milstead said. "... There should be no benevolence for this person, or apathy. This is a cold-blooded crime. This person is a coward."

No one has been killed in the shootings in the Arizona capital. There's been one injury: A 13-year-old girl whose right ear was cut late last month when a bullet pierced the windshield of the SUV in which she was riding, the DPS said. She was treated at the scene.

Read More