It was around 6pm on Sunday evening that the boy was found dead in an apartment in the Porsön residential area in Luleå.
The father was then arrested and detained as a reasonable suspect for the crime.
- The father is questioned and denies any crime, but we believe we have a picture of what has happened.
I cannot go into any details at the moment, says Lindha Strömberg.
The father of the dead 8-year-old was treated in hospital for his injuries but has now had to leave the hospital.
What caused the mother to raise the alarm?
- I can go into it at the moment, says Lindha Strömberg.
At the latest on Thursday at 12 o'clock, the prosecutor must decide whether the arrested person should be remanded in custody or released.