All the threats prove, is that the sniper deep down is simply a coward.
Considering a police phoneline call receiver hung up on him, it sounds as though he's also fairly unreasonable in daily affairs. It doesn't matter what is done with him, until he's under physical control this nutjob will be a deadly threat to any reasonable person.
He's not a coward if he took a shot over that cops shoulder. Stupid, yes.
Definately a very angry person. His reasons I heard were stated in the letter but that is known only to the police. I think the police KNOW that he is NOT Al Qaeda that is why they are not thinking in the realm of ME terrorists.