PHOENIX - A man questioned in a string of Phoenix freeway shootings is not the prime suspect and investigators are pressing ahead with leads in a case that has left the city on edge for two weeks, authorities said Saturday.

A 19-year-old man from a Phoenix suburb who was detained Friday at a convenience store near Interstate 10 is a person of interest, but Arizona Department of Public Safety spokesman Bart Graves declined to say what led police to question him. The man has been booked into jail on an unrelated marijuana possession charge.

"This is an open investigation, and we are going to go where it leads us," Graves said.

Many Phoenix drivers have avoided freeways since the 11 confirmed shootings began Aug. 29, mostly along I-10, a major route through the city. Eight of the cars were hit with bullets and three with projectiles that could have been BBs or pellets. One girl's ear was cut by glass as a bullet shattered her window.

Graves said the investigation was moving forward and authorities were not concerned about the public growing complacent now that someone has been questioned. Police were still seeking tips, with freeway message boards across the city continuing to flash a tip-line number.

Motorists have also been calling because they believe they've been targeted. Two incidents of cars that sustained shattered windows while on or near the I-10 were reported Saturday, according to DPS. But officials said one vehicle's damage was caused by road debris and the other by a street sweeper.

The shooting scenarios have varied. Some involved bullets fired at random cars, others involved projectiles and one was apparently road rage, Graves said.

Graves said Friday that investigators were questioning the man "about a number of things" besides the freeway shootings, but he declined to disclose what that entailed. People who answered phones registered to the man's address said they weren't related to him.

The man, who had his initial court appearance on Saturday, is being held in jail without bond because he had a warrant out for his arrest on a probation violation, said Deputy Joaquin Enriquez, a spokesman for the Maricopa County Sheriff's Office, which runs the county's jails.

The man pleaded guilty a month ago to an endangerment charge. He was set to be sentenced Thursday, but it's not clear whether that hearing took place. Enriquez said the man also was booked in May on an allegation of car racing.

A message left Saturday for Laura Anderson, his attorney in the endangerment case, wasn't immediately returned. He faces a Friday hearing on his probation possibly being revoked.

After being apprehended, the man told Fox 10, a Phoenix TV station, from the back of a squad car that officers surrounded him and his mother, guns drawn, after he bought a pack of cigarettes and a drink at a convenience store Friday. He said officers had been aggressive with him, aggravating his back injury.

Witnesses said law enforcement officers seemed to be waiting for the man to appear and moved in quickly, surrounding his white Chevrolet Tahoe with unmarked vehicles.

Store clerk Sara Kaur said she sold the man cigarettes, around 9:15 a.m., moments before between 15 to 20 cars swarmed in and officers handcuffed him. She described him as a regular customer, and she said she's "never had a problem with him."

Authorities have appealed for help through social media, news conferences, TV interviews and freeway message boards. Many of the thousands of tips proved to be false leads.

Longtime residents still remember a string of random shootings that terrorized Phoenix a decade ago. Nearly 30 people were shot then, 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.