The toll in the accident in which a van mowed down pedestrians near New York's Macy's department store rose to seven when a woman died from her injuries.
The elderly driver of the van has been questioned but not charged.
At least eight other pedestrians were injured when the vehicle ploughed into a crowded intersection on Herald Square, one of the city's prime shopping destinations.
Police said an officer had ordered the 76-year-old driver, Mr Sidney Weinstein, to move his vehicle because it was double parked during the evening rush hour on 34th Street, which was packed with tourists and shoppers. He was making a delivery at a nearby shoe store.
The van abruptly moved forward, striking several pedestrians, before it crashed into the back of a bus, police said.
Four people died at the scene, including a 15-year-old boy. Three others died in hospital.
Of nine other people taken to hospitals, at least two were in a serious condition.
One of the nine was Mr Weinstein himself.
Officials said he spent the night at New York Presbyterian Hospital but gave no details of his treatment.
The van was owned by Worldwide Distribution Services, of Secaucus, New Jersey police said. The company declined to comment.
A witness said the van hit pedestrians on a zebra crossing before striking the bus, and that some people were trapped between the two vehicles.
PA