Let’s not speculate. We just may never know. (Do I really need to add a s/ tag here?)
Talking heads are pushing the “lone wolf” BS while local networks here (a dozen miles south of where the murderer lived, and a dozen miles west of where he killed people) are showing a close-up of another Muslim they are seeking. Also, neighbors have made it very clear he was always with a couple of other killers - this is a cell.