They are all sharing one rifle? Does that seem right to you?
All of the bullets (excepting todays which wont be done with till tomorrow) that they have recovered enough of for study have had matching rifling marks on the jacket. Thats how they know they are dealing with a serial shooter.
Now he may have a partner. But a whole gang using only one rifle?
This is also the biggest argument against it being AlQaida. Why only one shooter using only one rifle? It still might be possible that its a AlQaida plot that hasn't gone off according to plan, and that the one segment is going on with it alone rather than give up and go home. But its a long shot.
If it was AlQaida I would expect multiple shooters striking simultainiously-or nearly so-in multiple, widely dispersed areas. They might use only one rifle per team-but their would be multiple teams, and then not all the bullets recovered would match, and the timing of some shootings would be impossible.