Police are not looking for anyone else in connection with the fire
A 10-year-old boy who died with his mother after a suspected arson attack by his father had suffered serious head injuries, police have said.
Ben Philpotts died in hospital a few hours after the fire in Trevarrian, near Newquay, on 18 January. His mother Patricia, 44, died in the fire.
Ben's father Harold Philpotts, 47, who was the prime suspect, suffered serious burns in the fire and died in hospital.
Cornwall's mental health authority said Mr Philpotts was known to them.
Det Insp Stuart Ellis, senior investigator for the case, said: "Initial investigations at the scene and the post mortem indicate that Ben suffered a serious head injury during the incident."
He said a serious case review was being discussed by the police, health officials and the local authority.
The chief executive of the Cornwall Partnership Trust, which provides mental health services, said she was "deeply saddened" by the "tragic fire".
Lezli Boswell said Mr Philpotts was known to the trust and her thoughts and condolences were with the families involved.
Mr Philpotts died in the early hours of Tuesday at Frenchay Hospital in Bristol.
No-one else is being sought over the deaths.