The incident happened outside of a Brooklyn cafe Friday evening, the New York Post reported.
As Atwater, 48, exited the cafe, a black Honda Ridgeline sports utility vehicle mounted the curb and pinned her against the building.
"She just came in to buy cookies. She looked happy, she was smiling," said the cafe manager, Alauddin Shipun. "She walked out. I heard a big bang and she was gone. Someone was trying to lift her head up and asking her, 'Are you OK? Are you OK?'"
Atwater was pronounced dead at Long Island College Hospital.
The 53-year-old driver of the vehicle may have lost consciousness because of diabetes, police said. He stayed at the scene and has not been charged.
Atwater, a Princeton University graduate, won an Emmy in 2009 for her writing on "WordWorld," a PBS kid's show. She was also nominated for an Emmy three years in a row for her work as a producer on "Clifford the Big Red Dog."