PARIS — The body of a missing young man was found in France’s Loire river this week, over a month after he disappeared at a concert where police fired tear gas to disperse the crowd, fueling anger over the use of force by the French police.

Steve Maia Caniço, a 24-year-old who ran extracurricular activities at a school, disappeared last month after attending a techno music concert on the banks of the Loire river, on an island in the western city of Nantes. His body was found on Monday a little over half a mile from the area where the concert had taken place.

Friends had suspected that Mr. Caniço — who they said did not know how to swim — had fallen into the river and drowned. As the police confronted revelers with tear gas after the concert, 14 people had to be rescued from the water. In the month he was missing, Mr. Caniço’s disappearance grew into a cause nationwide, as critics called it the latest example of excessive police tactics.

Hundreds of protesters gathered earlier this month in Nantes to form a human chain along the Loire river, asking, “Where is Steve?”