Mehdi Nemmouche, 29, was arrested Sunday after customs officials discovered a Kalashnikov assault rifle in his luggage and a revolver in a carry-on bag.
He was arrested at the St. Charles Train Station in Marseille, France, after taking a bus from Brussels to France, where he lives. Nemmouche is from Roubaix in the Pas-de-Calais region of northern France.
Officials also found ammunition, a black hood and gloves, a gas mask, a Nike cap and a blue nylon jacket, all items matching the description of the Brussels shooter.
On a file on a Nikon camera also found in the bag was a 40 second video showing images of the guns with audio commentary saying a recording of the shooting at the Jewish Museum using a GoPro camera didn't work.
An Israeli couple in their 50s and a French woman died in the shooting incident at the museum May 24. A fourth person, a museum worker, was shot and injured.
Nemmouche was described as a radicalized Islamist by Francois Molins, the chief prosecutor in Paris.