The accident occurred at about 5:30 p.m. on eastbound I-84, just past Exit 7, state police said. The driver of the pickup continued after hitting the pedestrian and took Exit 8 for Newtown Road, followed by the witness, state police said.
It was not clear why the pedestrian, identified as Susan Blaney, 53, of Brewster, N.Y., was on the highway.
State police found the suspect, Roger Leblanc, 43, of Torrington, in the his white 2005 Chevy Silverado pickup, in the parking lot of The Edge fitness club at 100 Newtown Road, state police said.
The state trooper administered a field sobriety test to Leblanc, who "did not perform to standard," state police said.
Leblanc was arrested and charged with operating under the influence, evading responsibility and second-degree manslaughter with a motor vehicle.
He was held on $500,000 bond with a court date of Friday, Dec. 23.
Blaney was transported to Danbury Hospital, where she was declared dead.
State police are investigating and witnesses are asked to call Trooper Diaz at 203-267-2240 at Troop A in Southbury.
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