I read his manifesto. It is written by a well educated person. Insane perhaps; clearly unreasonable in some places, but not stupid. On top of that we know that he spent some time with the Navy and became an officer, a lieutenant.
No person, not even the stupidest gangbanger, will head up a mountain in winter and then signal everyone that he is there by setting fire. The police must believe that he knows what he is doing. Probably he does. The police should be happy that he hasn't mined the area around the truck; probably he has no access to military explosives.
He can't do everything right, but I'm sure he had lots of time to build plans of revenge. I suspect those plans were his major thought for several years now. Even if only 10% of his bravado speech in that manifesto is true, he will be a serious opponent. He has only one problem, IMO: his physical characteristics (namely, size and weight) are quite distinctive.