The teenager has been charged with three counts of dangerous driving causing death after allegedly crashing a stolen Mercedes in the regional Queensland town of Maryborough on Sunday night.
The female victims have been identified in media reports as Michale Chandler, 29, Kelsie Davies, 17, and Sheree Robertson, 52.
A 23-year-old woman remains in a critical condition after being airlifted to a Brisbane hospital.
The 13-year-old boy is in police custody and due to face court in Maryborough on Tuesday.
Fraser Coast Deputy Mayor Denis Chapman said his community was in mourning.
"A lot of these people are well known through the community, like the nurse, a lot of the nurses work with her and said how lovely a person she was," he told Nine's Today program on Tuesday.
"People out there are just very upset over what's happened."
Queensland Police Union president Ian Leavers said the incident showed why the criminal age of responsibility should not be raised.
"We have states across Australia who want to raise the age of criminal responsibility to 14," he told Today.
"That would mean that 13-year-old would not be held to account."
Mr Leavers previously argued against raising the age after a Queensland Greens proposal to increase it from 10 to 14.
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