The mother of a teenage murderer sobbed after her son was sentenced to life in prison.

Armin Mehdikhani-Sarvejahani was sentenced to a minimum 17 year term in prison yesterday afternoon after he stabbed Mustafa Momand over a drug debt in Brighton on October 5 last year.

Mehdikhani-Sarvejahani, of Butts Road in Southwick, was described as an “expendable foot soldier” tasked with carrying out the planned attack.

After the sentencing at Lewes Crown Court, the 16-year-old’s devastated mother tried to walk around the front of the courtroom and was looking in the direction of Mustafa’s parents as they were leaving.The Argus: Armin Mehdikhani-Sarvejahani has been given a life sentenceArmin Mehdikhani-Sarvejahani has been given a life sentence (Image: Sussex Police)

She sobbed and screamed as a family member stopped her from getting any further.

A group of around 15 young men were also in court to support Mehdikhani-Sarvejahani.

Tensions flared outside the building and police were forced to stop traffic. A police car followed Mehdikhani-Sarvejahani’s parents' car as they left the court.

Mehdikhani-Sarvejahani wrote a letter to presiding judge Mr Justice Adam Constable KC although appeared emotionless as he was given a life term.

The Argus: Armin Mehdikhani-Sarvejahani chasing Mustafa Momand up Queen's Road armed with a kitchen knifeArmin Mehdikhani-Sarvejahani chasing Mustafa Momand up Queen's Road armed with a kitchen knife (Image: Sussex Police)

He said the letter showed the “smallest glimmer” that he understood the effect of his actions and the impact they have had on others.

"I have no doubt you left the house, having turned your phone off, with the knife, knowing Mustafa was in Brighton,” said Mr Justice Constable KC.

“These actions were definitely part of a planned attack. You took the knife for the purpose to at least cause serious harm.

The Argus: Tributes left at the scene for Mustafa MomandTributes left at the scene for Mustafa Momand (Image: The Argus)

“You forced him to run for his life, no doubt terrified in his last minutes of consciousness on this earth.”

Mr Justice Constable KC accepted that the brutal stabbing was done on the orders of someone higher up in the county lines operation that Mustafa was trying to escape.

The trial jury heard he was a marked man who had received death threats over a £20,000 drug debt which forced him to move out of Brighton.

Watch video of the moment Armin Mehdikhani-Sarvejahani was arrested by police:

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Mustafa had enrolled in college away from Brighton where his family thought he would be safer and only returned to the city for a court appearance at Brighton Magistrates’ on the day he was murdered.

He crossed paths with Mehdikhani-Sarvejahani in Queen’s Road on his way back to Brighton Station where he was going to get a train to a children’s home in Croydon.