The 40-year-old man, who was shot and wounded by police after lunging at the officer, had shouted that he was "a soldier of the caliphate" during the attack on Tuesday and that he was acting in revenge "for Syria".
The video pledging allegiance to the jihadist group was found in a police search of an apartment he was renting in Cergy outside Paris, the source in the investigation said.
Documents found on the attacker identified him as an Algerian doctorate student studying the media at a university in eastern of France.
Government spokesman Christophe Castaner told RTL radio on Wednesday that the attacker had "never showed any sign of radicalisation".
The attack was an "isolated act", he said.
The 22-year-old police officer sustained minor neck injuries in the assault in the packed square at one of France's most visited tourist attractions.
The attack comes as France is on high alert after jihadists killed seven people in London on Saturday.
Disclaimer: No Business Standard Journalist was involved in creation of this content
You’ve reached your limit of {{free_limit}} free articles this month.
Subscribe now for unlimited access.
Already subscribed? Log in
Subscribe to read the full story →
Smart Quarterly
₹900
3 Months
₹300/Month
Smart Essential
₹2,700
1 Year
₹225/Month
Super Saver
₹3,900
2 Years
₹162/Month
Renews automatically, cancel anytime
Here’s what’s included in our digital subscription plans
Exclusive premium stories online
Over 30 premium stories daily, handpicked by our editors


Complimentary Access to The New York Times
News, Games, Cooking, Audio, Wirecutter & The Athletic
Business Standard Epaper
Digital replica of our daily newspaper — with options to read, save, and share


Curated Newsletters
Insights on markets, finance, politics, tech, and more delivered to your inbox
Market Analysis & Investment Insights
In-depth market analysis & insights with access to The Smart Investor


Archives
Repository of articles and publications dating back to 1997
Ad-free Reading
Uninterrupted reading experience with no advertisements


Seamless Access Across All Devices
Access Business Standard across devices — mobile, tablet, or PC, via web or app
