Meanwhile, a driver and passenger were shot Tuesday while traveling on the Ohio Turnpike in Milan, about 90 miles north of Columbus. The 29-year-old driver was hospitalized in critical condition with a head wound, and the passenger was treated for a hand wound.
State Highway Patrol Sergeant Tom Curran said Wednesday that the turnpike shooting was an isolated incident and not related to the attacks near Columbus. One person was being questioned Wednesday but no charges had been filed.
Parents held their children's hands as they walked past police officers into the Hamilton Central Elementary School on Wednesday. Police announced Tuesday that they had linked the shootings, including one that killed a woman.
Superintendent Bill Wittman said he believes the shooting at the school was not meant to harm anyone because it happened overnight, but parents were nervous.
Michelle Maupin broke from routine and drove her daughter to school Wednesday. "We didn't put her on the bus because we felt it was too big of a target for whoever is doing this," she said.
At least four of the shootings — three at vehicles and one at the school last month — were from 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, investigators believe all 12 are connected, he said.
"We actually have 12 now with the school, and we're comfortable collectively that those 12 are linked," Martin said. He would not elaborate.
Authorities have received more than 500 tips, but would not speculate about who might be responsible and would not release the type of weapon.
The shootings began in May along Interstate 270, the freeway that circles Columbus. Many were not reported until after Nov. 25, when 62-year-old Gail Knisley was killed by a bullet that pierced the side of a car driven by a friend.
Hamilton Central Elementary in Obetz, about two miles from the freeway, was hit Nov. 11. Local businesses have established a $10,000 reward for information leading to an arrest.
The school sits along a rural road lined with pastures, three schools, a church and houses decorated with Christmas lights.
Tiffany Ellis, 32, said her son's second-grade classroom faces 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.
Edward Cable, whose rear window was struck Nov. 21 as he drove on I-270, is still unnerved about how close he came to death. But it's the fact that his little grandson was very nearly in the back seat that night that brings tears.
"He said … 'I'm riding with you,' and I said, 'No.' I just had a feeling that evening that he shouldn't," Cable told CBS News Correspondent Cynthia Bowers.
Last year, a three-week shooting spree in the Washington D.C. area left 10 people dead and three wounded. John Allen Muhammad, 42, was convicted last month of his role in the shootings and a jury recommended a death sentence. Fellow sniper suspect Lee Boyd Malvo, 18, is currently on trial in Virginia. If convicted, he could also face the death penalty.
Criminal behavior experts have varying opinions on who's behind the Ohio attacks. Jack Levin, a Northeastern University criminologist, believes 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.
"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 is the way I would describe it," he said.