French authorities opened an investigation after an aide to President Emmanuel Macron was caught on video assaulting a protester during the country's May Day demonstrations.
Paris prosecutors announced their probe into Alexandre Benalla on Thursday amid a public outcry over the incident on May 1.
The video shows Benalla, wearing a police helmet, dragging a woman away and then hitting a young protester and stomping on his stomach.
Al Jazeera's Sonia Gallego reports from Paris.
