Killer Kouachi and his brother shot dead by police after two-day manhunt

But he decided not to press charges after being threatened by Kouachi

He said Cherif Kouachi, 32, attacked him saying he should be 'ashamed'

Incident told by a former neighbour in Paris suburb of Gennevilliers

Attack: A neighbour of killer Cherif Kouachi (above) said he headbutted him for listening to pop music

Charlie Hebdo gunman Cherif Kouachi once headbutted his neighbour for listening to 'infidels' music'.

The extremist's violent past was laid bare by the man who said he was attacked by the 32-year-old and later threatened when he tried to press charges against him.

The neighbour, who did not want to be named for fear of reprisals, said Kouachi would often knock on his door and complain that he was listening to pop music, which he said was 'haram' or sinful.

The younger of the Kouachi brothers lived above the man in a seven-storey block of flats in Gennevilliers, a suburb in the north of Paris, for about seven years.

Kouachi, 32, rented the 300 Euro-a-month flat with his wife Izzana Hamyd, who was today released from custody.

Kouachi, who was shot down in a hail of bullets on Friday, banged on the man's door two years ago and said: 'Don't listen to such music anymore. This is the music of the infidels.'

The neighbour said Kouachi, who only listened to Islamic music and prayers, later confronted him in the street and threatened him, saying: 'Haven't you understood yet? You're still listening to infidels' music, you need to stop.'

The neighbour said: 'I answered, saying: 'I'm paying my rent, I have the right to listen to whatever I want.'

'And then suddenly he headbutted me really hard. I told him: 'You should be ashamed, you're a Muslim and you're religion tells you to respect others and to not be violent.'

Scroll down for video

The killer lived in the same block of flats as the neighbour in the Paris suburb of Gennevilliers (file photo)

He reported Kouachi to the police but was deterred from pressing charges after he received another late-night visit from him.

The neighbour said: 'When Kouachi found out that I'd reported him to the police he came back to tell me that if I went further with my complaint then I would hear from him.

'He told me: "I'm not alone. We will come for you."

Later another neighbour told the man that Kouachi had made plans to beat him up again.

Mrs Kouachi had confided in the woman saying that she had tried to prevent her husband from attacking him again.

Tributes: A growing mass of candles and flowers today outside Charlie Hebdo's offices in Paris

Cherif Kouachi and his brother Said were gunned down in a stand-off with police on Friday after a two-day manhunt and siege.

The extremists sparked global condemnation when they burst into the offices of the satirical magazine Charlie Hebdo and slaughtered 12 people, including a police officer outside the building.

Cherif, the younger of the two, was radicalised in his years living in the impoverished Parisian enclave of Gennevilliers with his wife.

With vast concrete blocks of state-owned flats and a population of around 10,000 Muslims, the vast majority of them from North Africa, the area has a history of tension with the French authorities.

Mohammed Benali, the president of Cherif Kouachi's local mosque, said the problem was not with those who had immediately come to France.

Solidarity: More than a million people paid their respects to the victims on the streets of Paris today

Instead it was those whose families had been there for several decades, but whom the authorities had made little attempt to integrate into wider society.

Mr Benali told the Daily Mail last week: ‘They saw how their parents were treated and felt deeply resentful.

'After the 2005 riots I was among a Muslim delegation who met Nicolas Sarkozy (then interior minister) and I’ll never forget his words.

‘He told me that “to humiliate is to radicalise” – and that is exactly what came to pass.

'This second generation felt excluded, discriminated against, and most of all, humiliated.