"He didn't know if Isaak was dead or alive when he went running out to the front of our house," she told the Herald today.
"Heaps of cars started stopping because the boys were in the middle of the road.
"Isaak was quite close to the car. He landed on the windscreen and flipped over the top. Jono was quite a way from the car."
The female driver of a small hatchback stopped at the scene.
She was said to have been "in major shock ... absolutely devastated". Her car was badly damaged.
Isaak suffered a fractured skull, brain injuries, broken legs, deep cuts to his face and throat, as well as glass in an eyeball.
Cath Strom said her son was in a stable, serious condition in intensive care at Christchurch Hospital.
Jonathan also broke both legs, as well as a broken pelvis.
Both boys are Rangiora High School students.
Cath Strom says she hasn't really been able to talk to Isaak yet.
She says they were at home on Saturday night and believes they were about to go for a walk.
Asked how she was faring, she said she was "a bit of emotional wreck ... better today because we know he's not going to die".
However, doctors say it's too early to say whether he'll make a full recovery.
"They're lucky to be alive ... [doctors] have said that a hundred times."
The police serious crash unit is investigating.
Both boys enjoy playing basketball while Isaak also loves trampolining, swimming, fishing, "normal boys sort of stuff", his mother said.
"Jono is getting a bit frustrated already," she said.
"These boys have a very, very long recovery."
• Givealittle pages have been set up for both boys:
