"It's believed they were run over by a car. At least one car, could be more," said Captain Mark Overwise, commanding officer of the Philadelphia Police Department's Accident Investigation Division.
The crash happened on Sunday at about 8 p.m. when 37-year-old Rebecca Malave was walking with her 3-year-old son Armani Negron along the 100 block of West Luzerne Street in the Hunting Park section of the city.
"911 calls were of woman laying in the middle of the street," said Overwise.
Malave and her son suffered serious blunt force trauma, police said. Investigators believe the two just left their house only a few blocks away.
"Between 7:30 p.m. and 8:00 p.m. she left her house to go visit a friend and she was found about 8:05 p.m.," said Overwise.
Both mother and son are now fighting to survive.
"They are critical, they are critical and they could use some prayers," said Overwise
The family says Rebecca Malave is in a coma at Temple University Hospital and faces possible paralysis.
"Awake, we need her awake," said her sister Lorraine Graulau.
Armani is stable but critical condition at St. Christopher's Hospital for Children. Family said his condition is improving.
The family wants to thank a passing stranger on a motorcycle for assisting.
"He grabbed my nephew while the EMS was still working on my sister to get her to the hospital," said the victim's uncle, Homi Malave. "Someone, whoever it is, we just want to thank you first of all. We just want to ask you if there is anything else that you know."
"We want you to know how appreciative we are because you saved a little boy's life," said Graulau.
Overwise said the stretch of West Luzerne Street is desolate, bordered by a cemetery and industrial area, and there weren't any surveillance cameras to capture the crash or aftermath.
Philadelphia police are asking anyone with information to come forward.