A four-year-old boy killed by an out-of-control 4WD was holding his father's hand as they left a Melbourne medical clinic when the horror smash occurred.
A Toyota LandCruiser went flying into the Epworth Specialist Centre car park in Berwick about midday on Friday.
The driver, a 56-year-old Pakenham man, told a witness he had just left the nearby Casey Hospital after receiving dialysis.
He is in a stable condition in Dandenong Hospital while paramedics took a woman in her 60s who was clipped by the car to Casey Hospital with minor injuries.
Detective Sergeant Mark Amos told reporters at the scene the father and son from Narre Warren South were walking out of the clinic when the boy was hit.
"The father's gone out with his son, holding his hand, doing what good dads do," he said.
"And this outcome's come up on them very, very suddenly.
"There's just no way you could've predicted this could happen."
Cameron and Sarah Smith were driving behind the LandCruiser when the crash happened and rushed to assist.
"He was in front of us and he started to veer off into oncoming traffic and he's gone airborne," Mr Smith told the Nine Network.
"He stated that he had dialysis, he just had blood taken out and he just literally pulled (out) from the hospital."
Photos from the scene show the Toyota LandCruiser on its side with a smashed windscreen, next to a number of smashed-up parked cars.
Several witnesses told reporters they saw the LandCruiser become airborne before crashing.
"It was off the ground, travelling at a huge speed and, of course, then I hear the slamming into the other vehicles," Michael Fleming told Nine.
"I ran around and I saw the little boy being held by someone. Couldn't even imagine the shock. Walking in a car park of a medical centre and this happens. Very sad."
An Epworth HealthCare statement said staff at the medical centre had helped where they could and are assisting police with their investigation.
"Epworth staff are shocked and saddened that a four-year-old child has died at the scene and that a number of people are injured," the statement said.