Ali David Sonboly (pictured) targeted innocent children at a McDonald's fast food restaurant in the city before he turned the gun on himself

Classmates have revealed how computer-obsessed Munich killer Ali David Sonboly called himself 'Psycho' and promised revenge on those who bullied him at school.

Sonboly, 18, targeted youngsters when he went on a rampage at a McDonald's fast food restaurant in the German city on Friday, killing nine people - seven of them teenagers.

He then attacked people near the Olympia Shopping Centre before he turned the gun on himself and was found to have 300 rounds of ammunition in his rucksack when police discovered his body.

A 14-year-old girl who lived in the same block of flats as Sonboly has now revealed how the murderer once told his classmates: 'I will kill you all.'

And during an argument just a few months ago Sonboly, who was today described as being 'deranged', had boasted about wanting to kill people in a massacre.

The young girl told the Daily Mail: 'He was not popular at school, he only had two or three friends that he would hang out with.

'In an argument, he said he wanted to carry out a massacre. He said: "I will kill you all".'

The girl said she saw Sonboly in the apartment block around midday on Friday - just hours before the shooting spree.

She added: 'He was just standing looking down. Usually he would say hello but he did not even look at me as I walked past.'

Meanwhile, another former classmate claimed he was bullied at school after shooting six men and three women during a rampage has revealed that the teenager 'always' promised revenge by 'killing' his tormentors.

The anonymous person - who went to the same school as the killer - posted online late last night that they knew the attacker.

A 14-year-old girl who lived in the same block of flats as Sonboly has revealed how the murderer once told his classmates: 'I will kill you all'

Sonboly was a 'loner, who had no qualifications and was 'obsessed' with violent first-person shooting computer games, using names like 'God like' and 'Psycho' on his online profiles

An anonymous person posted on a website - thought to be a chat room - that they went to the same school as Ali Sonboly

They wrote on a website, thought to be a chat room, that pupils 'always mobbed' Sonboly - which in German means 'bullied' - while he was at school.

The post read: 'I know this f****** guy, his name is ali sonboly. he was in my class back than (sic). we always mobbed him in school. and he always told us that he would kill us.'

It has since been deleted and comes after heavy-armed police raided Sonboly's home two miles from where the attack took place.

Munich police chief Hubertus Andrae described the killer as a 'classical shooter without any political motivation' and added that he committed suicide as he was not shot by police.

Police raided his parents' flat overnight and discovered the Iranian-German was reading documents about 'spree shootings' before he carried out the attack.

Sonboly used a Glock 17 semi-automatic handgun, which he got hold of illegally, to kill the victims - aged 13 to 45.

A video purporting to show the shooter, dressed in black, firing 20 shots has been posted on Twitter

Today, Germany mourned the young people killed yesterday, seven of whom were teenagers. People wept as they gathered at the site of the massacre to lay flowers today. The youngest victim was just 13 years old

Seven of nine dead victims were teens, including three aged just 14, and 27 people were injured. They were 13, 15, 17, 19, 20, 45, and 18, with the rest of the ages yet to be released.

Officers also found he had a book, Why Kids Kill: Inside The Minds of School Shooters, in his bag when he started firing at helpless children who tried to run away.

Sonboly, who claimed he was bullied at school, did not have a licence for the weapon he used - which is a popular firearm used by law enforcement agencies worldwide.

It also emerged today that the teenager received 'psychological treatment' and was interested in mass shootings after files were found at his parents' home, which was two miles from the scene.

The teenager was later seen having an argument with a man on a balcony after he carried out the despicable attack.

Teenager Najib Haupbuam (pictured) said he would often call at Sonboly's home to meet with his younger brother Daniel. He said Sonboly would stay hidden away in his room

Sonboly would rarely venture out of his room when visitors called at his 5th floor apartment in the Maxvorstadt district of the German city. The apartment block is pictured

A black mat with the word 'welcome' was outside the entrance to the green front door but neighbours said they had little to do with the killer

Neighbours said Sonboly's parents were hard working and always very pleasant to speak with. The family's name appears on a panelof buzzers for apartments in the block

He complained that had been bullied for seven years after he fired his weapon during the massacre which started in the fast food restaurant.

Sonboly was born Germany to a mother and father who had fled from Iran in the 1990s.

His father, Masoud, ran an upmarket taxi firm using a BMW series 7 limousine that he is said to have washed and waxed every week.

Sonboly's mother is said to have worked as a sales assistant in the Karstadt department store in the city.

He was put through a trade school in his early teenage years when it became apparent he was unlikely to complete the standard German Abitur exams.

But he ended up failing at his school too, blaming bullying by 'Turkish and Arabic' schoolmates as being the reason for his poor educational performance.

Lacking any academic qualifications, he was then seemingly doomed to a life of shelf stacking or floor washing.

Over the years his resentment grew while the warped fantasies he developed were fuelled by violent video games he played on sites where he gave himself profile names like 'Psycho' and 'God Like.'

One gaming site called Steam even banned him after his temper grew increasingly volatile and he began to insult fellow gamers.

An electrical shop next to the shopping centre was being used as a makeshift hospital to treat the casualties after the incident

The scene was flooded with flowers and messages of sympathy. This card in the Olympic quarter in Munich reads 'rest in peace, we will miss you'

He was said to abusive and threatening in the cyberworld while he also started to receive psychiatric therapy to battle his demons in the real world.

One online gaming friend reportedly said: 'We kicked him out of the online group over a year ago because he kept threatening us,' said one of his online gaming buddies.

'But he kept inventing new identities to sneak back in.'

The mentally ill loner spent hours locked in his bedroom playing violent video games, according to a family friend.

Sonboly would rarely venture out of his room when visitors called at his 5th floor apartment in the Maxvorstadt district of the German city.

Instead, the 18-year-old who stay behind the closed door playing games like 'Call of Duty'.

Teenager Najib Haupbuam said he would often call at Sonboly's home to meet with his younger brother Daniel. He said Sonboly would stay hidden away in his room.

Off-duty doctors and nurses were summoned to hospitals in Munich, with a hospital spokesperson telling DPA: 'The alarm for a "mass attack" has been triggered'

'All he would do all day is play the shooting games. He was obsessed with them and wanted to be the best. He would go online for hours and play Call of Duty' Najib told MailOnline.

'I did not know him that well, no one really did as he did not mix much.'

Najib ,14, said the only time Sonboly would join in a conversation was when talked turned to the video game 'Call of Duty'.

'That is the only time he wanted to join a conversation,' he said. 'He had no interest in nothing else. He wasn't interested in girls and did no go out much in the evening.'

Najib said Sonboly delivered papers to blocks of flats in Dachauer Street and was paid up to 90 Euros a month.

The salary from the part time job would have allowed Sonboly to purchase the Glock pistol privately.

Sonboly's deadly rampage in targeting children bears a chilling comparison to that of another mass killer who shocked the world in 2012.

Adam Lanza went on the rampage at Sandy Hook Elementary School in Newton, Connecticut in the US killing 20 children and six teachers days before Christmas in 2012.

He had prepared for his shocking killing spree by obsessively playing the first person shooter game 'Call of Duty.'

THE CONVERSATION BETWEEN THE MUNICH MALL SHOOTER AND A MAN ON A BALCONY WAS CAUGHT ON CAMERA In another video on social media a man can be heard yelling at suspect in the car park that he is a 'w*****' and an 'a******e.' And he yelled: 'Put your gun down.' Balcony man: 'You fucking a*****e you...' Gunman: 'Because of you I was bullied for 7 years...' Balcony man: 'You w****r you. you're a w****r' Gunman: '...and now I have to buy a gun to shoot you' Balcony man: 'A gun! F**k off! Your head should be cut off you a*****e' The gunman and balcony man begin shouting at each other. Balcony man apparently to people filming: 'He's got a gun here the guy has one' Unseen voice: 'F*****g Turks!' Balcony man: 'F*****g foreigner' Balcony man to someone else: 'Ey! He's got a gun! He has loaded his gun. Get the cops here. He's walking around here the w****r!' Gunman: 'I am German.' Balcony man: 'You're a w****r is what you are' Gunman: 'Stop filming!' Balcony man: 'A w****r is what you are. What the f**k are you doing?' Shooter: 'Yeah what, I was born here.' Balcony man: 'Yeah and what the f**k you think you're doing?' Gunman: 'I grew up here in the Hartz 4 (unemployment benefits in Germany) area.' Balcony man and Shooter talk at same time. Balcony man: 'Yeah treatment is something for you' Gunman: 'I haven't done anything here for (unintelligible) ... 'Please shut your mouth' Balcony man: 'You c**t you' Balcony man to people nearby: 'Hey, he's on the upper floor here.' The cameraman goes into cover as the gunman starts firing. Balcony man calls him a c***t again. Balcony man: 'They must have been s******g into your head' Gunman: 'They have not. They have not, that's the thing. They have not.' Advertisement

Lanza, 20, was mostly isolated from society and spent hours in his blacked out bedroom. He took his own life before he could be arrested or disarmed by police.

Haupbuam said Sonboly had few friends at school and never attempted to mix.

'I know his brother very well but we never went around with Ali. He was just not interested.'

Sonboly lived with his parents in a fifth floor flat bock of flats mostly occupied by other immigrant families.

A black mat with the word 'welcome' was outside the entrance to the green front door but neighbours said they had little to do with the killer.

They said his parents were hard working and always very pleasant to speak with.

'They worked very hard and I had no complaints about them,' said one neighbour who declined to give her name.

'We are just so shocked. There are many children who live in the block and he seems to have deliberately gone after young children.

Police also confirmed that the killer hacked a young woman's Facebook page in a bid to lure some of his victims to their deaths with a promise of free fast food.

In the post, he advertised the offer and told youngsters to gather at the restaurant to take advantage of the offer.

At around 4.50pm, the black-clad shooter - whose mother works in German department store Karstadt - burst from the toilets in the fast food restaurant and began 'killing the children' with a pistol, witnesses said.

He then continued his bloody spree in a local shopping centre and on the streets around Munich's Olympic quarter.