Sentencing Dyson Allen to life, Mr Justice Males said he had no motive to harm the children or anyone in the Smith family.
So why did you do it? In one sense, what prompted you to do this terrible thing - not only starting a fire in a room where defenceless young children were asleep but waiting for several minutes before raising the alarm - is a mystery.
But in another sense, why you did it seems clear enough.
It was because you were out of your head due to the lethal combination of alcohol and cannabis which you had taken that day and because of your fascination with fire, particularly when you are affected by drink or drugs.
A teenager will be sentenced today over the deaths of four siblings from a house fire.
Four-year-old twins Holly and Ella Smith and their two-year-old brother Jordan were asleep as the blaze took hold in Freckleton, Lancashire, while elder brother Reece, 19, was overcome by fumes as he went upstairs to try to rescue them.
All four died from the effects of smoke inhalation from the blaze on January 7 last year.
In July, Dyson Allen, 19, was convicted of four counts of manslaughter by a jury at Preston Crown Court who found he had set fire to a bedroom wardrobe. He was cleared of the siblings' murders but was told by a judge that he would face "a substantial prison sentence".
Lancashire Fire & Rescue Service said the blaze in Freckleton, Lancashire, was "one of the most tragic fires" they have ever attended.
Group manager Mark Hutton said: "Working closely with forensic scientists, scenes of crime officers and other experts, the investigation was painstaking in its detail.
"Whilst we are deeply saddened by the loss of life we are reassured that our collective ability to mount such a full, thorough and professional investigation has contributed to the verdict announced today."
A statement by the family of four siblings killed in a house fire has paid tribute to the son who tired to save his brothers and sisters.
A statement from Michelle Smith, the children’s mother, Martin Goulding, Reece’s father and the rest of the family said:
“We are pleased that Dyson Allen has been convicted of the manslaughter of our beautiful children Reece, Holly, Ella and Jordan.
"We’ll never know the reason why our children were taken from us but even knowing the answer won’t bring them back.
"He had the chance to explain his actions to the police and the court but he lied from the very beginning.
“We would like to thank the fire service and other emergency services who tried to save the children that night.
"We would especially like to thank the police for their determination in bringing him before the courts and for the outcome that we now have today. That outcome has only been reached because of the help and support given to the police by people who have been willing to give evidence.
“Finally though, we would like to pay tribute to Reece who paid the ultimate price for trying to rescue his brother and sisters and for that we will be eternally grateful and proud.”