A 65-year-old man was driving in the eastbound lanes around when someone in another vehicle rear-ended him and started shooting, according to ISP.
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That driver then left the scene.
The victim's car was hit by the gunfire but the man was not, officials said.
The shooting closed down all eastbound lanes from Half Day to milepost 23 for several hours while police investigated.
State police are still looking for the shooter. They're asking for anyone who saw what happened to call them.