QUESTIONS today began to emerge about why an ISIS gunman who shot a cop dead in Paris was free to carry out his attack.

Karim Cheurfi, 39, killed traffic cop Xavier Jugele, 37, and injured two more after opening fire with a Kalashnikov on the the Champs-Elysées last night.

He had been jailed for trying to kill two policemen and this year was found with knives and masks he claimed was for a carnival.

41 Karim Cheurfi, who carried out the deadly shooting, was questioned two months ago over threats to kill a police officer Credit: Splash News

41 Xavier Jugele, 37, was today named as the traffic cop killed in the terror shooting

41 Three policemen have been shot - one dead - on the Champs-Elysees in Paris Credit: Reuters

41 Police remove the body of a policeman who was shot dead as he sat at the wheel of his van Credit: Vantage News

41 Forensics officers search a grey Audi thought to have been driven by the assailant Credit: Reuters

41 The gunman is said to have shot through the window of a parked police van Credit: AP:Associated Press

41 Emergency services line up on the Champs-Elysees near the Arc de Triomphe Credit: EPA

Details have since emerged of how the Islamist had only two months earlier been questioned by cops about threats to kill a police officer.

He was taken into custody on February 23 of this year and his home was searched. Hunting knives and masks from the film Scream were found.

But Paris prosecutor Francois Molins said: "These elements were not sufficient to provide proof that he wanted to carry out a threat of assassination. For example, he said the masks were for a local carnival."

It has also emerged the killer was jailed for 20 years in 2001 for trying to kill two policemen - but only served 15.

ISIS claimed responsibility for the attack after the killer got out of a car next to a parked police van and opened fire through the window before officers returned fire and shot him dead.

41 Heavily-armed police were on the streets of Paris this afternoon Credit: Getty Images

41 The French capital is on a high state of alert following a series of terror attacks Credit: Getty Images

41 President Francois Hollande visited French cops today Credit: Reuters

41 The outgoing premier also paid a visit to hospital treating those wounded in the attack Credit: Reuters

Traffic officer Jugele was today named as the policeman killed in the shooting. A female foreign tourist was also wounded.

Jugele, 37, had been caught up in the city’s 2015 Bataclan Theatre massacre where 90 died.

He had said when it reopened: “We’re here to say no to terrorists.”

He was shot in the head when Cheurfi pulled up in an old grey Audi, leapt out and opened fire on cops near a police van.

Passers-by fled as the killer was shot dead by police.

Cops have since raided his Chelles home in the hunt for clues about accomplices.

Weapons including a hunting rifle and knives were found in his car along with a Koran, the addresses of intelligence agents and details on a police chief.

A note defending ISIS was also found next to his body.

41 Investigators were today scouring the Chelles home of the alleged shooter in a bid to uncover clues Credit: News Group Newspapers Ltd

41 A French police searched the Chelles property is was revealed he had been on their radar in the months leading up to the attack Credit: News Group Newspapers Ltd

41 Cops are now in a race against time to find out if the attacker had any outside help Credit: News Group Newspapers Ltd

The terror group has since claimed responsibility for the attack and named the gunman using his alias Abu Yousif al-Belgiki - Arabic for 'The Belgian'.

Cheurfi was previously jailed for 20 years for shooting at cops after he was caught driving a stolen car in Roissy-en-Brie in 2001.

But he was released early following an appeal ruling.

Police said he had been detained in February after threatening police but freed soon after.

French cops investigated him over reports that he had been talking about killing police officers and was getting weapons.

He was found to have hunting knives, masks and a GoPro camera in his possession but this was not thought sufficient proof of his deadly plans.

Cheurfi was born on New Year's Eve in 1977 in the Livry-Gargan suburb in Paris' north east.

A repeat offender, he had been jailed four times for attempted murder, violence and theft.

In April of 2001 the killer shot a plain clothes policeman while driving a stolen car.

He was caged for that offence and emerged from prison in October 2015, five years earlier than he was sentenced to.

A neighbour said: “He was a lost soul. He did not pray, he drank and watched jihadist propaganda.”

This morning a Belgian man French cops said they were also hunting in connection with the attack handed himself into a police station in Antwerp.

41 Bullet holes were pictured in the windows of surround buildings following the shooting Credit: AP:Associated Press

41 Daylight revealed the damage inflicted on the streets of the French capital Credit: Reuters

41 The bullet-ridden police car was taken away for investigation last night Credit: Rex Features

The 35-year-old had been described as "very dangerous" and was reported to be in possession of firearms and a train ticket from France, Le Parisien reported.

The attack sparked calls for voting to be suspended in Sunday's French presidential election. Candidates were debating live at a nearby television studio when the gunfire began.

Last night, police are said to have found guns and ammunition when they raided a house in the eastern Paris suburb Chelles - the family home of 39-year-old suspected extremist Karim Cheurfi.

Three members of his family are in police custody, local media reported.

A number of other raids were also carried out across the French capital.

The grey Audi allegedly used in the shooting was registered to Cheurfi, according to documents seen by the Associated Press.

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Recently he was questioned after alleged threats to buy weapons and kill policemen over the encrypted messaging app Telegram, according to reports.

Intelligence sources said the dead assailant was a known radical on a so-called S-file, for "State-security".

It means he would have been under surveillance, because he was a known risk to the country.

Isis mouthpiece Amaq said the killer uses the name Ben Yousef al-Belgiki - meaning the Belgian - although Cheurfi is believed to be French-born.

Local police advised people to avoid the area after shots were fired at around 9pm local time.

A witness named Chelloug said the attacker pulled up beside a stationary police vehicle and fired through the window.

He said: "He parked just behind the van and he got out with a Kalashnikov and I heard six gunshots.

"I thought they were firecrackers, because we all looked around the road and there was no one.

"In fact, he was hidden behind the van and shooting at the police.

41 A police alert for suspect Karim Cheurfi, who is listed as unemployed Credit: Splash News

41 Diners cowered in a restaurant as shots rang out on the Champs-Elysees Credit: MEGA

41 Armed police told people to stay inside after a terrorist opened fire with an AK-47 Credit: MEGA

41 President Francois Hollande holds an emergency cabinet meeting this morning at the Elysee Palace in Paris Credit: Reuters

41 Forensics officers collect evidence from the car used by the Kalashnikov killer Credit: AP:Associated Press

41 A man raises his arms in front of police officers close to the scene in Paris Credit: Getty Images

41 A police van at the scene in Paris, where a policeman has been shot Credit: Reuters

41 The suspect's car was seen being towed away last night after an inspection by forensic police Credit: AP:Associated Press

"I think he hit a policeman. As soon as the policeman opened the door of the van, he fell, I think.

"As soon as we saw that, we all ran back inside (a building). We hid and I went up to the first floor and we saw them (the policeman) shoot him (the perpetrator)."

He added: " I was afraid. I have a two year-old girl and I thought I was going to die... He shot straight at the police officer."

The officer who died was at the wheel of the van and was eating an evening snack, according to reports.

President Francois Hollande said officials were "convinced" the incident is a terror attack, even before ISIS claimed responsibility.

Paris Prosecutor's anti-terror office has opened an inquiry.

41 The shooting took place at the iconic Champs-Elysées boulevard in central Paris

41 Emergency crews fill the famous shopping street, a hub for tourists that runs from Place de la Concorde to the Arc de Triomphe Credit: EPA

41 Police on high alert after three officers were shot in Paris Credit: EPA

41 Women raise their arms as they head towards armed police Credit: Getty Images

Yvan Assioma of the police union Alliance said: “The exact circumstances are still unclear but I can confirm the tragic death of one of our colleagues. Our thoughts are very much with the family.

“One or several attackers have been shot dead by the police. Some officers were hit but the bullets were stopped by their bulletproof vests, but two were hit.

“Nothing is being ruled out for the time being, terrorism or a criminal act."

41 The Eiffel Tower is seen behind police cars as cops hunt the area Credit: AP:Associated Press

41 As police car at the scene in Paris, where a police officer has reportedly been killed Credit: Twitter/James Mate

41 A soldier stands guard in front of the illuminated Arc De Triomphe Credit: Getty Images

A Government spokesperson said: "An automatic weapon was used against police, a weapon of war.

"The shooting started shortly after 9pm, when a car stopped alongside a stationary police car.

"A man immediately got out and opened fire on the police car, fatally wounding a police officer. He also wounded a second one, it would seem very seriously."

The shooting happened near the Métro station Franklin D Roosevelt and the Marks and Spencer store on the Champs-Elysées.

It is one of the most famous streets in the world and a busy tourist hub.

Armed police and emergency services flooded the area overnight. By this morning the streets had been washed clean of blood and rush hour traffic returned to normal in a city where shootings have become depressingly routine.

41 Passersby raise their arms as they pass the scene Credit: EPA

41 An armed policeman stands guard with the Arc de Triomphe in the background Credit: Reuters

41 Emergency services at the scene of a fatal shooting in Paris Credit: Sky News

41 Members of the public have been advised to steer clear of the area Credit: Getty Images

41 A police cordon is in place around the scene Credit: Getty Images

Mr Hollande has scheduled an emergency meeting following the shootings.

French Presidential candidates Marine Le Pen and Francois Fillon have cancelled their trips tomorrow.

The attack comes just days after police arrested two men in southern Marseille with weapons and explosives who were suspected of preparing an attack to disrupt the first-round of the presidential election on Sunday.

41 A soldier guides people away from the scene in Paris Credit: Reuters

41 A police officer close to the Arc De Triomphe in Paris Credit: AP:Associated Press

41 Armed police at the scene in Paris Credit: Getty Images

41 Emergency services rushed to the scene in Paris Credit: EPA

France is in a state of emergency and at its highest possible level of alert since a string of terror attacks that began in 2015, which have killed over 230 people.

The UK Foreign Office said: "The British Embassy is in contact with local authorities and urgently seeking further information following reports of a shooting incident on the Champs-Elysees in Paris.

"You should remain vigilant and follow the advice of the local security authorities and/or your tour operator.

"If you're in the area and it is safe to do so, contact your friends and family to tell them you are safe."

US President Donald Trump yesterday addressed the atrocity at a news conference.

He said: "It looks like another terrorist attack.

"It just never ends."

Last night in Paris, several major metro stations were closed and the centre of Paris was still in lockdown.