While the perps may be Muslims, I wouldn’t assume that it is Jihadists. Without knowing more details, it feels like a gang hit at first glance. Marseille is infested with organized crime.
Jihadists are looking for mass killing, driving a big truck through a crowd (as in Nice) is more cost effective for them. When they do use firearms, as in Paris, San Bernardino, and Orlando, they go for big crowds and a high body count.
That could be, and the presumption is rebuttable. But I think all investigations of these kinds of senseless mayhem and murder should begin with the presumption of the perps being Islamic Jihadists. Over the years almost all large-scale senseless mayhem and murder have proven to have been perpetrated by Islamic Jihadists.