CNN) -- Ohio investigators learned Tuesday that ballistic tests have positively matched two prior incidents to the weapon used to kill an elderly woman riding as a passenger on Interstate 270 before Thanksgiving.
There are now four cases positively linked to the weapon, announced Chief Deputy Steve Martin with the Franklin County, Ohio, Sheriff's Department.
Since May, there have been 11 shootings along Interstate 270, which circles Columbus, Ohio. Investigators suspect they may all be related to the same shooter, or shooters.
A 12th shooting took place November 11 at a school, rather than along Interstate 270 like the other 11. However, the incident took place at 1:35 a.m., when no one was there.
The shooting at the school, "takes this person or persons off of (Route) 23 or off of (Interstate) 270 and puts them more in a residential area," Martin said.
Motorists travel down Interstate 270 Sunday in Columbus, Ohio, where a woman was shot and killed last Tuesday.
The four cases linked through ballistics are the shooting of a freight truck October 19, the shooting at the empty school building November 11, a shooting along Route 23 November 23 and the most recent shooting November 25, which killed 62-year-old Gail Knisley.
Knisley -- the only casualty so far -- was hit by a single bullet as she was being driven on the highway, about 10 miles south of Columbus, to a doctor's appointment. She was taken to a hospital, where she died shortly afterward.
Martin reiterated his plea Tuesday to residents to inform authorities of anything that might be suspicious. He said more than 225 leads have been called in so far, and none are considered too small or too insignificant.
In addition to the Franklin County Sheriff's Office, the investigation includes the FBI, the Bureau of Alcohol, Tobacco and Firearms, the Columbus Police Department and the Ohio State Highway Patrol.
Meanwhile, the police presence remained beefed up along Interstate 270.
Damn imagine getting shot at in your car going down the highway damn
There are some fucked up people in this world. I hope they catch the shooter and give them the injection.
