Emergency services were called to the car park at Nepean Hospital near Penrith about 3.20pm after the crash.
Police said a woman in her 60s allegedly reversed into another car before hitting a pedestrian, a woman believed to be in her 40s, in the carpark on Derby Street in Kingswood.
“The driver and pedestrian were both assessed by NSW Ambulance paramedics; however they were pronounced dead at the scene,” NSW Police said in a statement.
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“The driver of the other car – a woman believed to be aged in her 30s – was treated by hospital staff for shock.”
It’s believed the driver suffered a medical episode before she crashed into the pedestrian.
Police are investigating the incident.