The search for a suspect in a string of Phoenix freeway shootings has taken on a frenzied pace, with a panicked public flooding a police hotline with tips.

Police confirmed one of these reports as a shooting, raising to 11 the number of vehicles struck on Phoenix-area freeways since Aug. 29. Eight were hit by bullets and three by projectiles such as BBs and pellets.

One girl's face was cut by glass as a bullet shattered her window.

Authorities are appealing for help through social media, news conferences, TV interviews and freeway billboards. The messages have morphed from "report suspicious activity" to "shooting tips" to the more ominous "I-10 shooter tip line" on Thursday.

Thousands of tips have come in, many proving to be false leads based on road hazards routine in Arizona, like windshields cracked by loose rocks sent airborne by the tires of other vehicles.

On Thursday alone, drivers reported possible shootings of an armored truck, two cars and two tractor-trailers. Authorities and TV crews scrambled to these scenes, only to discover minor damage.

Only one of these proved to be a shooting, Department of Public Safety spokesman Raul Garcia said. A commercial truck driver found a bullet hole in his cargo area after making hours of deliveries, so it was impossible to know where or exactly when it happened.

As the shootings intensify and get more attention, many drivers are taking alternate routes.

Ron Freeman, who works at a truck stop near Interstate 10, said he called his wife and family and told them to stay off the freeway until the situation calms down.

"It's kind of spooky, man, when people can't drive up and down the interstate unless they're getting shot at," Freeman said.

The shootings haven't fit any obvious pattern. Most happened on Interstate 10, a main route through Phoenix. Bullets have been fired at various times of the day, striking a seemingly random assortment of vehicles, from an empty bus to tractor-trailers to pickup trucks, cars and SUVs.

Helicopters flew up and down Interstate 10 on Thursday as an officer monitored a wall of TV monitors carrying live surveillance video from every freeway in metro Phoenix. The Arizona Department of Public Safety has enlisted the help of the FBI, Bureau of Alcohol, Tobacco, Firearms and Explosives, local police and undercover law enforcement officers.

"We have a number of officers ... both uniformed, non-uniformed, plainclothes, undercover vehicles, marked vehicles on the road patrolling, looking for the suspect, looking for leads," said Bart Graves, another DPS spokesman.

Many longtime Phoenix residents still remember the random shootings that terrorized the public a decade ago. Nearly 30 people were shot, and eight killed, including a cyclist who was riding down the street and a man who was sleeping at a bus stop. Two men were eventually caught and convicted.

These shootings also recall other random highway and roadside shootings, most notably the sniper attacks that terrorized the nation's capital more than a decade ago before two men were captured there.

Sheriff Zach Scott of Franklin County, Ohio, knows exactly what Arizona authorities are going through.

He was a lead investigator when drivers were frightened by Ohio freeway shootings over several months in 2002 and 2003, one of them deadly. They set up an emergency operations center and staffed a task force from 10 different agencies to field calls, taking in more than 5,000 tips.

The most valuable one came from a relative of Charles McCoy Jr., who called to report that "I got a nephew who acts crazy and has a gun and might have something to do with this," Scott recalled.

McCoy fled to Las Vegas and was arrested there on St. Patrick's Day 2003.

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AP writers Jacques Billeaud in Phoenix and Sadie Gurman in Denver contributed to this report.