A group of up to five men broke into the 45-year-old woman's Bankstown home, in Sydney's southwest about 10.30pm on Thursday and severely assaulted both her and her son, before she was dragged into an SUV.
That car was later found burnt out in Beverly Hills, about 6km away, with a body discovered inside after fire crews extinguished the blaze.
Superintendent Rodney Hart said the body was so badly burnt a visual identification was impossible, but police strongly believe it is the 45-year-old who was kidnapped.
Authorities cannot rule out that the woman was burnt alive.
"This crime is horrendous, the level of violence is unheard of," Supt Hart said.
"But I want to reassure the community we strongly believe this is a targeted incident and this has not been a random kidnapping."
Authorities were called to the Bankstown house about 10.30pm on Thursday after the kidnapping was reported.
They were told a group of people had broken into the property and kidnapped the woman.
Police say the kidnappers, who had firearms, assaulted an eight-year-old boy with a baseball bat before forcing the woman into an SUV.
The eight-year-old underwent surgery for serious head injuries and remained in an induced coma in ICU, in a serious but stable condition.
His 15-year-old brother, who has provided police an account of the ordeal, was also taken to hospital for assessment.
Having spoken with him on Friday morning, police believe their father was interstate on a business trip.
"He has spoken to police, and he's on his way back to Sydney now to support his two children and to assist police with their inquiries," Supt Hart said.
"The two children are our main focus, their welfare and their security is paramount to us."
Police do not know how the group of men were known to the 45-year-old, or if the incident was gang or organised crime-related.
They will undertake a "very large" CCTV search canvassing the 6km between the two crimes scenes, appealing for members of the public with relevant information or video footage to come forward.
"We have put all available resources on this strike force so that we can assure that we will do the best for these children and the husband," Supt Hart said.
Crime scenes have been set up at both the house where the kidnapping occurred and at the burnt-out car.
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