THE brother of a murder victim stabbed an innocent stranger to death in a brutal shopping centre killing.

John Paul Bird knifed John Bulloch in the heart when the victim attempted to stop him hassling two women for a cigarette.

Mr Bulloch stepped in after he heard Bird threatening to gouge out the women's eyes for trying to ignore him.

A jury watched harrowing footage of the 40-year-old being attacked before staggering to his death at Glasgow's Springburn Shopping Centre in May last year.

Bird denied murder, claiming he could not control his actions at the time due to an "abnormality of mind".

But, the 30 year-old was convicted of the charge following a trial at the High Court in Glasgow.

Bird - who has a long history of violence - was locked up for a minimum of 18 years as a judge paid tribute to the "public spirited" Mr Bulloch who lost his life trying to help.

The killer was jailed eight years after his brother Jason was knifed to death in the city's Balornock area.

Father-of-two Mr Bulloch - who lived with his elderly gran - was struck on May 3 last year.

Nicola Jackson told the jury how she had been standing outside the shopping centre smoking with friends when Bird approached.

He asked for a cigarette and Ms Jackson, 28, told him no, but Bird became aggressive.

Miss Jackson recalled: "He said he was either going to stab me or my friend in the eye if one of us did not give him a draw of a cigarette.

"I asked him to go away. He kept asking and asking - he wasn't leaving where we were."

Mr Bulloch heard what was happening and stepped in.

Miss Jackson said she remembered Mr Bulloch saying to Bird: "Why are you speaking to females like that - she has asked you to please go away. Just please go away."

But, Bird - armed with a blade - quickly turned on Mr Bulloch.

Miss Jackson told the court: "He put a hand in his pocket and pulled the knife out of his pocket - he just stabbed him."

The horror was caught on CCTV and footage showed a bleeding Mr Bulloch stagger inside the shopping centre before slumping to the ground.

He had been stabbed in the heart.

Lawyers for Bird had lodged a special defence at the trial claiming he had an "inability to control his conduct" at the time due to an "abnormality of mind".

His mother Angela gave evidence and claimed Bird had been badly affected since the murder of his 16-year-old brother Jason who was stabbed to death in 2007. Three people were later convicted in connection with the attack.

Mrs Bird told the court: "He just became very withdrawn - he just seemed down all the time. He became depressed."

But, after the verdict the the jury heard Bird had a long criminal record with convictions for assault, robbery and possession of offensive weapons.

Judge John Beckett QC jailed Bird for life.

He told him: "The public-spirited Mr Bulloch intervened (that day) and asked you to leave the women alone and encouraged you to move away.

"It is crystal clear that he offered you no violence or threat.

"As a result of your inexcusable and gratuitous violence - with no warning - Mr Bulloch lost his life and his family lost forever the man of whom they have every reason to be proud."

Jennifer Harrower, Procurator Fiscal for Homicides and Serious Crime in the West of Scotland, said: "This was a senseless crime and Bird has left devastation and sadness in his wake. He now faces spending the rest of his life behind bars."