As many as 12 recent shootings along a five-mile stretch of Ohio interstate highway near Columbus are connected, investigators said Tuesday. 

The incidents date back to May, but the widely reported death of 62-year-old Gail Knisley on Nov. 25 has resulted in terrorized drivers in the Columbus area for the past week and a half.

Four November shootings — three at vehicles and one at an elementary school — involved the same gun, Franklin County Sheriff's Chief Deputy Steve Martin said Tuesday.

Although ballistics tests could not link the rest of the shootings along Interstate 270 (search), which circles Columbus, investigators said they "are comfortable" saying all 12 were connected, he added.

Despite having received more than 500 tips, authorities would not speculate about the shooter's identity and would not reveal the weapon used.

"Collectively, we think it's not good for us to put that information out," Martin said.

Many of the shootings were not reported until after the death of Knisley, killed by a bullet that pierced the side of a car driven by a friend.

The latest incident linked to the others was a Nov. 11 shooting at Hamilton Central Elementary (search) in Obetz, about two miles from the freeway. The school sits along a rural road lined with pastures, three schools, a church and houses decorated with Christmas lights.

Nervous Hamilton Central parents said they didn't want to change plans despite news of the school's involvement.

Greg Mellon said he hoped recreation basketball practice would calm the children, including his 8-year-old son Corbin, who was so frightened on the way to practice that he cowered under the dashboard.

"He ducked down in the car," Mellon said. "Of course he's worried about it."

Jimmy Eggers said he brought his 8-year-old son to the basketball practice Tuesday night because "it's hard to stop your daily routine." But he added: "It's definitely scary. You fear for your kid's life."

Hamilton Central Superintendent Bill Wittman said he believed the nighttime shooting was not meant to cause injury, but parents were less reassured.

Tiffany Ellis, 32, said her son's second-grade classroom faced the front of the school, where the bullet struck.

"It makes me angry, to be honest with you, that I have to drive down the road worrying about getting shot," Ellis said. "That's kind of scary to think someone could shoot through your window like that."

Beverly Evans, whose Hamilton General Store is about a half-mile from the school, said she got "the chills" when she heard about the shooting and had become apprehensive about strangers.

"We watch them more closely and the car they're driving," Evans said.

She said her customers are frightened as well, "trying to figure out how to stay off 270, but now people aren't sure if that will keep us safe."

A house was shot at Tuesday near the freeway, but Martin said investigators have not linked it to the other shootings.

Local businesses have established a $10,000 reward for information leading to an arrest.

'It Scares Me'

At a gas station along the interstate two miles from Hamilton Central, emotions ranged from skittish to calm among drivers fueling up.

"The odds are you're not going to get shot," said Tom Dixon, 56.

Richard Bailey, 32, disagreed. He uses I-270 each day to get to his job as a shipping manager at Rickenbacker Airport.

"I drive through with my cell phone in my hand every day," he said. "It scares me."

A driver and passenger were shot and wounded Tuesday while traveling on Interstate 80 in Milan, about 90 miles north of Columbus. A dispatcher with the Erie County Sheriff's Department told Fox News the incident was not connected to the Columbus-area shootings.

The driver was taken by helicopter to Toledo's St. Vincent Mercy Medical Center (search) with a head wound. The passenger suffered a hand wound and was released from a hospital. One person was being questioned in the shooting, authorities said.

The Mind Behind the Attacks

Criminal behavior experts have varying opinions on who might be behind the attacks. Jack Levin, a Northeastern University criminologist, believed two people could be responsible.

"When I see a crime like this, it's almost always two friends who probably wouldn't do this separately, but when they're together there's a certain chemistry, a certain insanity," said Levin, director of Northeastern's Brudnick Center on Violence (search).

"How do you share the joy of killing or causing problems if you're alone? You can't brag about it or someone will turn you in," he said.

But N.G. Berrill, a psychologist who profiles killers at his New York forensic consulting firm, said the shooter is probably a young male who feels frustrated and generally powerless in his life.

"It's almost an infantile rage," he said, adding that the shootings seemed to be the work of a person who loves the thrill of causing panic, although he may not intend to kill.

The shooter is likely someone from the surrounding community, said Lou Palumbo, a retired police investigator who runs a private security and investigation organization called The Elite Agency Limited.

"He didn't have to travel far. He's got a certain comfort level with that landscape which could be what's allowing him to be drawn back to the same location of the shootings," Palumbo said.

Martin, the chief sheriff's deputy, said investigators were not relying on a psychological profile and had been exploring all possibilities.

Fox News' Steve Brown and The Associated Press contributed to this report.