A teenager who laughed after killing a shopkeeper with one blow after he refused to sell him cigarette papers was today branded a 'time bomb' after being locked up.

Vijaykumar Patel, 49, died when the 16-year-old boy, who cannot be named for legal reasons, launched the fatal attack because he was not sell him Rizlas.

But the senior detective who led the investigation today insisted that the four-year sentence handed to the boy for the attack in January was not long enough.

Mr Patel suffered devastating injuries when his head smashed into the ground in January

Vijay Patel, pictured with his wife Vibha, died after a 16-year-old boy launched a fatal attack

It emerged at the boy's sentencing hearing at the Old Bailey that he had had five alcoholic drinks at a party before the attack took place in Mill Hill, North London.

Mr Patel, who had his hands in his cardigan pockets when he was hit, suffered devastating injuries when his head smashed into the ground.

CCTV footage then showed the teen, who went into the shop with two friends, laugh as he ran away.

He was handed an extended prison sentence of four years. Mr Justice Jeremy Stuart-Smith said: 'He's a time bomb.

'The record, the facts of this case, the contents of the pre-sentence report with the analysis of causing significant harm. I don't find the pre-sentence report surprising,'

Mr Patel, pictured with his wife, had his hands in his cardigan pockets when he was hit

Members of the teenager's family, including his mother, watched on from the public gallery as he was led away by two dock officers after he was sentenced.

Speaking after the sentencing this afternoon, Detective Chief Inspector Luke Marks said: 'We were hoping the sentence would be perhaps more than it was.

Mr Patel was 'in the wrong place at the wrong time', according to the defence barrister

'However, the judge has set out his reasons for why he believed that was to be the sentence that was passed down.

'He's got previous convictions for violence, he's demonstrated with this offence he will react extremely aggressively to situations.

'I would agree with the judge he does pose a significant risk to members of the public.'

The boy was found guilty of manslaughter after a trial heard Mr Patel 'had not really been involved' in the confrontation outside the shop before the attack.

The boy 'launched himself' at Mr Patel and smashed him with his right arm, causing him to fall back and hit his head.

Representing the boy, Philippa McAtasney said Mr Patel was 'in the wrong place at the wrong time' and described the attack as a 'shove'.

But the judge said: 'Describing it as a shove does not do it justice in my view. He deliberately went to the left and launched himself.'

Mr Patel died in the unprovoked attack outside this store (in blue) in Mill Hill, North London

Mr Patel was pictured on CCTV at the shop in London just half an hour before he was killed

He added: 'He certainly intended to hit him very hard.'

After Mr Patel hit the ground another shop worker chased the boys off with a broom and billboard sign, the trial was told.

What Mr Justice Jeremy Stuart-Smith told the boy during sentencing 'I accept that you didn't go to the shop looking for trouble. 'I also accept that although you were offensive to the shop manager as you left you didn't at that stage have any intention of taking things further. 'When you were outside the shop and the manager and Mr Patel came out I accept that the manager was 'in your face' - not unreasonably given his understandable concerns. 'Mr Patel was well away from you and was not doing anything, either to you or generally, that might affect you. 'The CCTV shows he was simply standing with his hands in his pockets doing nothing.' He added: 'What happened next was that you deliberately moved to your left and launched yourself at Mr Patel, knocking him off his feet and to the ground. 'He was completely defenceless and didn't move before you struck him. The force of your attack is clearly shown on the CCTV. 'The assault was completely unprovoked and was directed at a victim was defenceless.' Advertisement

The bleeding shopkeeper was rushed to hospital but died the following day despite the desperate efforts of medics.

Detectives who searched the boy's bedroom found a coat with Mr Patel's saliva on the sleeve and a Burberry scarf he was wearing at the time of the attack.

The court was told the boy had also once attacked a teacher at school.

Miss McAtasney said: 'He's assaulted a teacher at one point but not gravely, there was no weapon.'

The boy had 'punched and kicked the teacher away' as he was being led down a corridor at school, she said.

She said the boy has ADHD, low intelligence and 'misconstrued the situation' outside the shop.

He had been at a party before the attack, she said, adding: 'He makes it clear in the [pre-sentence] report that he had five drinks.'

She claimed the boy 'thought Mr Patel had a knife.'

But the judge said: 'In my take on the evidence as viewed objectively on CCTV, Mr Patel was not doing anything, he was not fiddling, he was not fidgeting.'

The boy was told he would serve at least two-thirds of the sentence and would be subject to a period of three years on licence after his release.

The judge said the boy had a 'terrible record', including two incidents of being in possession of an offensive weapon and another for attacking a teacher.

He said a pre-sentence report 'concludes there is a high risk of reoffending.'