She did not believe the blaze was started intentionally.
An investigation into the circumstances of Caldwell's death found three boys from a nearby property had been visiting Caldwell's flat at the invitation of a woman known to and living with Caldwell.
The findings note the woman appeared to have suffered mental illness and substance abuse problems. Her behaviour was described as "erratic" and she was frequently seen sniffing a substance believed to be petrol.
On the afternoon of the fire the three boys had been invited back to the flat by Caldwell's flatmate, who after some time left the boys to their own devices and lay down on her bed. She and Caldwell had separate rooms, hers downstairs and his upstairs.
Around 8pm the boys were seen in the grounds of a nearby school, and shortly after, neighbours near Caldwell's flat heard loud noises.
Fire crews were called to the scene and neighbours attempted to dampen down the blaze in the interim. At this point, Caldwell's flatmate was described by witnesses as being seen running around outside the flat upset and crying.
The fire was burning so intensely it was not possible at this stage for firefighters to get inside in an attempt to save him.
Bruce Cole of the Fire Service concluded from a fire investigation that it started in the lounge area of the flat on the north side of the lower level. A lack of smoke detectors and available ventilation were noted as factors contributing to the spread.
Na Nagara said the fact three key witnesses to the incident were children, along with the victim's flatmate's mental health issues made the investigation "difficult".
The lack of finding as to the identity of the person who started the fire did not reflect badly on the police, she said.
