Islamic State militants, who had claimed being behind the attack in which a French policeman was shot dead, had named the attacker as Abu Yousif al-Belgiki.
The gunman, who was shot dead by police, had a long criminal record, a source close to the investigation told CNN.
After Thursday's attack, both Fillon and Le Pen announced that they would cancel events planned for Friday, the last official day of campaigning.
While serving a 10-year sentence, he also shot and wounded a prison officer after grabbing his gun.
Investigators searched a home early Friday in an eastern suburb of Paris believed linked to the attack.
The French have identified the man as a troubled 39-year old who had previously served time for the attempted murder of three police officers in 2001, and who was on the security service's watch list.More news: Rex Tillerson declares end to 'strategic patience' with Iran
Speaking Friday on RTL radio, Macron said: "What our attackers want is death, symbolism, to sow panic (and) to disturb a democratic process, which is the presidential election".
The attack happened when a vehicle pulled up next to a police van, with a gunman getting out and immediately shooting at officers who were guarding an area near the Franklin Roosevelt metro station.
After Le Pen spoke scathingly Friday of the government's fight against extremism, Cazeneuve said Le Pen's party in 2014 voted against an anti-terrorism law and, in 2015, against a law that beefed up resources for French intelligence services.
Interior Ministry spokesman Pierre Henry Brandet earlier told radio station France Info that officials found a shotgun and knives in the suspect's auto, and three people from his family were being questioned.
The prosecutor added that the man had nothing to do with the attack.
The attack appeared to fit in a spreading pattern of French extremists targeting security forces and symbols of the state, to discredit, take vengeance and destabilize.More news: United Kingdom delays decision on Sky merger approval
Police at the scene said they were searching for a potential second assailant, and Interior ministry spokesman Pierre-Henry Brandet said it could not be ruled out that there was another or others involved. He said one police officer was killed and two others were seriously injured and hospitalized.
Several candidates in Sunday's presidential election ended their campaigns early as a mark of respect, with the centre-right's Francois Fillon calling on others to do the same. "What can you say?"
Marty Cisse, an office cleaner from Mauritania, worries that Le Pen's closed-borders platform would threaten immigrants like himself, but said "security is important" and said it should be the priority of the next president.
Quoting President Donald Trump, Pence said "we have to be strong, and we have to be vigilant".
ISIS swiftly claimed the attack was carried out by one of its "fighters".
The identity of a man responsible for a shooting in central Paris remains unclear and there is no indication he was Belgian, Belgium's federal prosecutors said on Friday.More news: Man City's Jesus in line for Wembley return against Arsenal
France has been under a state of emergency for almost a year and a half, with more than 230 people killed in jihadist attacks since the start of 2015.
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