The rescue service was alerted to the apartment in Nacksta after a fire, a dead woman was found in the apartment.
Early on, suspicions arose that the fire had been started.
A few hours later, the now suspected man was arrested undramatically by police in central Sundsvall.
District Attorney Jens Göransson requested that the man be detained on probable cause on suspicion of murder and aggravated arson and the court now went along the prosecutor's line.