Hedi, a Frenchman of Algerian decent, walked past some uniformed thugs, and one shot him in the back of his head with a "less lethal" weapon.

The weapon did not kill him, but maimed him instead. It also knocked him down, which gave the whole group of thugs a chance to beat him up. He may have lost the sight of his left eye.

France did the right thing, quickly prosecuting all of those thugs. Whether it is necessary to keep the shooter in jail until trial, I am not sure. When a non-thug is accused of such crimes, refusing bail is justified if there is a danger that that accused will commit more crimes, or flee justice. I can't judge a priori whether that is the case here.