One of two woman struck by a dark-colored pickup truck that fled the scene Saturday morning in the Jefferson Park neighborhood has died on her 82nd birthday, authorities said.

Witnesses said the truck hit the women so hard, it threw them to opposite sides of the street.

Margaret Hefferman, of Niles, was pronounced dead at 12:26 p.m. at Advocate Lutheran General Hospital in Park Ridge, according to a spokeswoman for the Cook County Medical Examiner’s office. The spokeswoman said her birthday was Sept. 17, 1929.

Jefferson Park District police Lt. John Lewison said the surviving woman, 78, was in critical condition.

It makes no sense -- it’s a terrible thing," said Lt. John Lewison said. "We’re all sad here."

A black pickup truck drove off after hitting the two women shortly before noon, as they walked across the 5700 block of West Lawrence Avenue.

The truck, a black or dark blue Ford F-150, was being driven by a man and was last seen eastbound on Lawrence. The truck had ladders on it and a spare tire on its rear right axle. The driver was wearing dark clothing, according to a Jefferson Park District police sergeant.

Police spokesman Darryl Baety said driver was described as being in his late 20s or early 30s.

Contrary to preliminary reports, neither of the two women were nuns, police said.

The police Major Accident Investigation Unit is investigating.