Driver Graeme Schoneville, 26, and Michael Hendry, 22, were competing in the Highland Car Club Snowman Rally when he lost control of his Honda Civic in Glenuquhart Forest in Balnain, Inverness-shire.
The car flipped over after it left the track on a hairpin bend before crashing into a tree and landing on top of 50-year-old Joy Robson and the boy.
About 20 people worked to free the spectators, but Mrs Robson, a nursery teacher from Portree on Skye, later died. The child was taken to Raigmore Hospital in Inverness. His condition is not thought to be life-threatening.
Reports suggested that the boy's father had insisted on them standing behind the tree because he thought it would be safer.
It is unclear when officers from Northern Constabulary plan to speak with Mr Schoneville, from Carluke, South Lanarkshire, and co-driver Mr Hendry about the incident.
A spokesman said: "Members of the Force's Road Policing Unit will be carrying out a full road collision investigation and a report will be submitted to the procurator-fiscal."
The organisers, the Scottish Rally Championship, abandoned the event and extended their sympathies to the families of those involved after the crash on the opening nine-mile leg of the rally, five miles west of Loch Ness.
A Stage Rally event, it was organised under the auspices of the Motorsports Assocation (MSA), the national governing body.
A statement on the MSA website said: "As with any serious incident in or around UK motor sport, the MSA is now working closely with the organising club, the police and other agencies to establish precisely what happened on this occasion.
"The Motor Sports Association would like to stress that safety and risk management are the foremost considerations in each of the 5000 motor sport events organised each year in the UK and the sport has an excellent track record in this respect."
Mr Schoneville is an experienced rally driver, who in 2011 was given the opportunity to compete against leading drivers from across Europe at the RACMSA Rally of Scotland.
When not competing in events, he works for his family's SAAB dealership in Glasgow. He was unavailable for comment.
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