Investigators believe 89-year-old driver Robert Laine was driving through a festival at a train crossing in New London, Conn., when he hit a pedestrian at a slow speed and then plowed into the crowd.
"All of [a] sudden this wagon, this car here just came out of no place, just knocking people down and running them over," a witness said to ABC News.
Twenty-seven people were injured, and many suffered broken bones. One former paramedic at the scene said that the shaken driver told her his gas pedal had gotten stuck.
Laine told The Associated Press that he was "upset. I'm very upset."
This latest incident casts another spotlight on senior drivers.
In 2003, an 88-year-old man allegedly plowed into a crowded farmer's market in Los Angeles, killing 10 people.
Three years later, the legal fights continue in that case. The driver goes on trial in September charged with 10 counts of vehicular manslaughter. He says he accidentally stepped on the gas instead of the brake.
AAA says while elderly drivers are most likely to wear their seat belts and not drink and drive they still find themselves at risk.
"Seniors have the highest crash fatality rate of everyone except teenagers because of their fragility," said Mantill Williams, an AAA spokesman.
Researchers at the Massachusetts Institute of Technology's Age Lab say that fragility is the key.
"Issues that have do with your cognitive and mental ability have to do with how you drive safely. Age has nothing to do with whether or not you have an accident," said Joseph Coughlin, the lab's director.
Experts say relatives should go for a drive with elderly loved ones and observe whether they seem confused behind the wheel. Also check to see whether they are accelerating and braking at the right times and whether they get lost.
There are no consistent laws from state to state regarding older drivers. In fact only four states require road tests.
For more information visit seniordrivers.org.
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Reported by ABC News' David Muir on "Good Morning America."