Video report by ITV News Europe Editor James Mates
French officials have named the man who shot dead a policeman and wounded three other people in an ambush in central Paris as Karim Cheurfi.
Here is everything we know about him.
Who was Karim Cheurfi?
The apparent attacker was a 39-year-old French national who lived in the suburb of Chelles, to the east of Paris.
He had a long criminal history and was known to police.
Cheurfi launched a surprise attack with a Kalashnikov targeting police officers at the famed Champs-Élysées boulevard in the capital's centre.
He shot dead one officer, named as 37-year-old Xavier Jugele, and left two others wounded. A female tourist also suffered minor injuries.
Cheurfi was was shot dead at the scene.
What motivated the attack?
Initial reports suggest that both extremism and hatred towards police may have played a role, though investigators have stressed they are still establishing a motive.
The prosecutor confirmed that Cheurfi carried a note expressing sympathy for the so-called Islamic State group, which was found near his body, while a Koran was in his car.
It also emerged that he had a long criminal history including previous attacks and threats towards police officers.
Cheufi was convicted of attempted homicide over the shootings of two police officers in 2003.
He was also recently detained, reportedly for threatening police, but was released due to lack of evidence.
Was Cheurfi identified as a potential radical?
It seems that he did not cross the radar of authorities as a possible religious extremist or other radical despite extensive contacts with police and prison officials.
"He was not on the security watch list and had shown no signs of radicalisation despite his many years in prison," Paris prosecutor Francois Molins told a news conference on Friday.
Did Cheurfi have links to extremist groups?
That is still extremely unclear.
IS claimed that it was behind the attack in a statement made shortly after news of the shooting broke - but apparently misidentified the gunman.
The terror group said the gunman was one of their fighters, but wrongly identified him as a Belgian, throwing doubt on the truth of their statement.
Police are still trying to establish if Cheurfi had any contact or training with extremist groups.
They said that Cheurfi had travelled to Algeria in January and February, but the reason for those visits are not yet known.
Did Cheurfi have accomplices?
French officials believe that Cheurfi carried out the shooting single-handed, but are still trying to establish whether he had supporters or accomplices in planning the crime.
Three family members of the slain gunman have been detained, and searches are ongoing at his former home.
Another man flagged by Belgian security services in connection with the shooting attack has handed himself in to police in Antwerp, the Belga news agency reported.