PARIS (WASHINGTON POST)- French authorities identified a small-time criminal, apparently inspired by the Islamic State in Iraq and Syria (ISIS), as the perpetrator of a deadly attack on police officers in a shooting that set France on edge and darkened the final day of campaigning in the country's pivotal presidential election.

One police officer was killed and two others were seriously injured when a gunman, formally identified on Friday (April 21) as Karim Cheurfi, opened fire with a Kalashnikov assault rifle on a police patrol parked on the French capital's best-known thoroughfare, sending pedestrians fleeing into side streets. The ISIS claimed responsibility.

Cheurfi was then shot dead as he tried to escape, Paris prosecutor François Molins told reporters. Investigators subsequently found a number of knives and a pump-action shotgun in Cheurfi's car, as well as a message apparently scribbled in support of the ISIS.

The note praising the extremist group apparently fell out of Cheurfi's pocket, Molins said, adding that pieces of paper with addresses of police stations were found in his car.

Cheurfi, a 39-year-old of Algerian descent who was born in the Paris suburbs, had a criminal record and was well-known to authorities, Molins said.

In a profile that mirrored those of the perpetrators of other recent smaller-scale attacks, Cheurfi had been convicted at least four times since 2003 and had spent nearly 14 years in prison for crimes ranging from burglary and theft to attempted murder.

In 2001, he fired on and wounded two men, one of them a plainclothes police officer, who were chasing him as he drove a stolen car. He was released from prison in October 2015 and lived with his mother in an eastern suburb of Paris.

Earlier this year, French authorities became aware that Cheurfi had sought to purchase weapons and had made statements about wanting to kill police officers. As recently as April 7, Molins said, authorities had interviewed Cheurfi following a trip to Algeria. However, a judge decided not to revoke his probation.

Cheurfi's former lawyer, Jean-Laurent Panier, told BFM TV on Friday that his client was "extremely isolated" and a "psychologically fragile character" whose problems went untreated.

He said Cheurfi never spoke about religion, adding that he talked mainly about "how to fill his daily life with video games."

The slain police officer, identified as Xavier Jugelé, 37, was a member of the lesbian, gay, bisexual and transgender (LGBT) police officers and had spent his entire career in Paris, police officials said.

In November, according to L'Express newspaper, Jugelé had attended a concert that reopened the Bataclan Theatre, the main target in a series of ISIS attacks on Paris in November 2015. "This concert is meant to celebrate life," he told People magazine. "To say no to terrorists."

The attack was claimed with unusual speed on Thursday night by the ISIS through its affiliated Amaq News Agency, which said it was carried out by a Belgian national it identified only by the pseudonym Abu Yusuf al-Baljiki.

But authorities and analysts urged caution in interpreting that claim."It's never happened in the past so quickly," said Jean-Charles Brisard, an intelligence expert and director of the Paris-based Centre for the Analysis of Terrorism, referring to the ISIS tendencies in claiming attacks.

"Perhaps the individuals in question had some kind of coordination and were in contact" with the Islamic State, he said, "but we should also not rule out the possibility that Amaq was too hasty in releasing its statements."

Regardless of calls to expel all those in what sometimes is called France's "S File," a list of approximately 10,000 names that authorities suspect of potential Islamist radicalism, Cheurfi was never included in that file.

According to Molins, at no point in his long period of incarceration did he "show signs of radicalisation or proselytism."

"Now, it is a matter of determining the precise context of the act and possible complicities in its execution," he said.

It was not immediately clear whether the timing of Thursday's attack was linked to the French presidential election. But it appeared that way to many French voters, coming as the 11 candidates in the race were speaking in a widely watched televised debate.

Despite a promise not to campaign following the attack on Thursday night on Paris's renowned Champs-Élysées boulevard, far-right candidate Marine Le Pen reinforced her anti-immigrant message in a Friday speech, calling on the French government to immediately reinstate border checks and expel foreigners being monitored by the intelligence services.

"My government of national unity will implement this policy, so that the republic will live, and that France will live," she said at an impromptu news conference.

Prime Minister Bernard Cazeneuve rejected early calls to postpone Sunday's first round of voting, telling reporters that "nothing should hinder this fundamental democratic moment for our country."

He pledged heightened security, including deployments of heavily armed soldiers from a two-year-old counterterrorism campaign called Operation Sentinelle, as French voters go to the polls.

In Washington, President Donald Trump waded into France's political morass with predictions that the Champs Élysées attack would "have a big effect" on the election and would "probably help" Le Pen, who has raised many of the same anti-immigrant and security issues that Trump promoted during his campaign.

The election has become a critical test of strength for Le Pen and her National Front party at a time when nationalism has overshadowed other votes in the West, including Trump's victory and last year's British referendum on leaving the European Union.

Le Pen's opponents, meanwhile, have urged France to stand against the hard-line rhetoric that has dominated her campaign.