Sentencing, Judge Lady Hood said statements from Mr Rollinson’s family described him as “a true gentleman with a heart of gold and a wonderful husband and father”.

She said the family were “devastated by their loss” and that because of the circumstances of his death, they were unable to be with him when he died.

Lady Hood added: “Nothing said or done here today and no sentence I can pass will ever be enough to help Mr Rollinson’s family with their devastating loss.”

The teenager, dressed in a white shirt and black trousers, showed no reaction as he was led from the courtroom.

“The attack is not intentional to blame”

Earlier, Shelagh McCall KC, barrister for the young man, told the court that the attack on Mr Rollinson “was not intentional nor was it foreseen by the accused”.

“The incident was precipitated by an action by the deceased which appears to have been a trigger,” she said, referring to Mr Rollinson taking the young man’s phone and then stamping on it.

She told the court this reduced her client’s level of culpability, but admitted “the harm caused was of the highest order”.

Ms McCall also said her client understood the gravity of his actions and showed “sincere remorse” for it.

Sue Webber, Scotland’s shadow transport secretary, said: “Keith Rollinson’s death was a terrible tragedy and my thoughts are with his family today.

“Too many bus drivers are being put at risk and left feeling unsafe at work because of the SNP’s failure to crack down on this behaviour.

“Their lenient attitude means judges’ hands are tied because of youth sentencing rules, which meant a lighter sentence was handed down simply because of the offender’s age.

“John Swinney needs to get tough on those who think it’s acceptable to abuse our bus drivers and that should start by imposing restrictions and curfews on those abusing the young person’s bus pass scheme.”