A fifth victim wounded in the shooting attack at the Christmas market in the French city of Strasbourg died on Sunday, AFP reported, citing authorities and relatives.
The prosecutor's office confirmed that a Polish national had died after being injured by Cherif Chekatt in Tuesday's rampage.
"My brother Barto Pedro Orent-Niedzielski has just passed away. He thanks you for the love and strength you have given him," the brother of the 36-year-old victim from the Polish city of Katowice wrote on Facebook.
Chekatt, 29, attacked Christmas market shoppers armed with a gun and a knife, before being killed by police two days later.
On Thursday, French authorities shot and killed Chekatt. He was spotted leaving a building in the Neudorf area of the city, where he lived. After firing on police, he was killed as they responded.
The death toll in the attack, originally at three, rose to four on Friday when an Italian journalist succumbed to his wounds.
Orent-Niedzielski and his Italian friend Antonio Megalizzi, who was the fourth victim in the attack, had tried to stop Chekatt from entering a bar during Tuesday's assault, a close friend told AFP.
After Chekatt was eliminated, the Islamic State (ISIS) jihadist group claimed responsibility for the attack, saying in its propaganda news agency Amaq that Chekatt was an ISIS "soldier" who "carried out the operation in response to call to target citizens of the international coalition."
However, France's interior minister dismissed the ISIS claim, according to AFP.
Eleven people were wounded in the attack, with several still in critical condition.
French authorities continue to investigate the attack. On Saturday, four family members of Chekatt were released from custody, but three more people close to him are still being held.