The attack targeting police officers on Thursday in Paris' Champs-Elysees avenue may provoke "a burst of citizen mobilization and revive the spirit of January 2015", Madani Cheurfa, secretary-general of the Political Research Center of Paris Institute of Political Studies (Sciences Po) has said.
The couple were to spend one more night in Paris before flying to Scotland, and Mr Heuser said he didn't think the incident would put them off their travel plan.
France began picking itself up Friday from another deadly shooting claimed by the Islamic State group, with President Francois Hollande convening the government's security council and his would-be successors in the presidential election campaign treading carefully before voting this weekend.
The Islamic State group claimed the shooting, days before French presidential elections, via its Amaq news agency, naming the attacker as Abu Yousif the Belgian.
In addition to the assault rifle used in the attack, a pump action shotgun and knives were in his vehicle, the police sources said.
Shortly after the attack on Thursday night, several French media reported that the Belgian authorities had notified France of the probable arrival in Paris on Thursday morning of a 35-year-old Belgian.
Cheurfi served 10 years in prison after firing on two plainclothes officers in 2001 as they tried to arrest him in a stolen auto.
The Paris prosecutor's office got a tip in January that the gunman behind a shootout on the Champs-Elysees that left one police officer dead and two others wounded was amassing an arsenal and that he had made death threats against law enforcement.
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Interior Ministry spokesman Pierre-Henry Brandet said officers were "deliberately" targeted.
One police officer is dead and another hurt following a shooting in the French capital, police sources say. Three members of his family were detained for questioning.
As the first details of the attack filtered through, US President Donald Trump said that "it looks like another terrorist attack".
On Friday, French authorities said a suspect sought by Belgium police, who was suspected of having planned to travel to France on Thursday, had handed himself in at a police station in the Belgian city of Antwerp.
President Donald Trump, who has also taken a hard line against illegal immigrants in the US, tweeted early Friday about the Paris shooting, implying the latest bloodshed could Le Pen.
He noted that since then 80,000 people have been turned away at border checks, while 117 people have been deported from France for "terrorist activities". Security is high preceding the vote after police said they arrested two men Tuesday in what they described as a thwarted terror attack.
Sunday's vote is the first round in the French elections, with the top two candidates advancing to a winner-takes-all runoff on May 7.