An 18-month-old boy was killed along with an elderly driver who careered off a busy main road and ploughed into the toddler and his mother, police said.
The boy and his mother, believed to be in her early 20s, were on Water Street in Accrington, Lancs, when the 89-year-old driver mounted the kerb and crashed into them yesterday.
The trio were taken to the Royal Blackburn Hospital where the child and the driver, who is from Accrington but has not yet been named, died.
The toddler's mother, from Accrington, is in a critical condition. She is being treated for multiple injuries and was being transferred to the Royal Preston Hospital last night.
Lancashire Police appealed for witnesses who might have seen the driver's green Rover in the run-up to the crash.
A police spokesman said: "The car has come off the road at Eastgate, it has mounted the pavement and collided with a building at the bottom of Water Street.
"Sadly, it collided with a female pedestrian and a baby.
"The driver of the vehicle, woman and baby were all transported to the Royal Blackburn Hospital and unfortunately the driver of the car, an elderly man, and also the baby believed to be 18 months, have sadly died.
"The mother of the child is still being treated for multiple injuries and is in a critical condition."
Sergeant Pete Sculpher, from Accrington Road Policing Unit, said: "This is a tragic incident and our thoughts go out to both families involved.
"The collision happened on one of the busiest roads in Accrington at a time when many people would be picking children up from school so I would ask anyone that saw anything to come forward and speak to police."
Witnesses should call Lancashire Police on 08451 25 35 45 or 01254 51212.