HAVERHILL (CBS) – Police are looking for whoever tossed a rock onto a car driven by a great-grandmother on I-495 on Friday afternoon.

WBZ NewsRadio 1030′s Doug Cope reports.

Police believe the rock thrown from the Route 97 overpass at 77-year-old Dottie Whitten’s car was about the size of a baseball.

“I know it wasn’t like a bird hit it or anything like that,” said Whitten.

The rock broke the windshield, and Whitten said she then struggled to keep control of her car.

“I mean, I could have swerved and had another car hit me. I could have wound up on the side of the road someplace upside down,” said Whitten.

Whitten said she glanced into her rear-view mirror and spotted two or three teens on the bridge before pulling off the highway and calling 911.

Police went to the scene, but didn’t find anyone.

“They’re not thinking. That’s the problem. Kids do things and they don’t think of the consequences,” said Det. Bill O’Connell of the Haverhill Police Department.

Dottie says she’ll be looking up when she drives under a highway overpass from now on.

“You know people have gotten killed from kids doing that… I was very lucky,” said Whitten.

Police said the incident happened a short distance from Haverhill High School around 3 p.m., after school got out.

Anyone with information is asked to call police.