There are a number of questions that must be answered to validate the "lone nut" scenario:
1) Where did this kid obtain the high-grade explosives used in this bombing?
2) Did this kid do any test explosions anywhere to make sure his bomb would work? If not, why was his bomb so powerful on the first attempt, or did someone else give the bomb to him?
3) Did anyone who lived in his building notice that he was working with blasting caps, explosives, or written plans for a bomb? If not, when and where did he design this bomb, and if he didn't design it then who did?
4) Why did "authorities" tell an AP writer that the bomb was "attached to his body"? How could anyone know for sure that the bomb was attached to his body and he wasn't carrying the bomb?
There are a lot of unanswered questions in this case. Nothing can be ruled out based on what WE know at this time.
Your #4 stood out to me, too.
The AP report states the bomb was attached to his body. That leaves out the innocent bystander hypothesis.
Probably filming an episode of CSI: Oklahoma City.
Anyone with 1/2 a brain could cook up some nitroglycerin. (I had a friend who used to do this and blow up stumps.) All kinds of info on the Internet about how to make explosives.
Go to your local sporting goods or gun shop that sells reloading supplies. A 1 lb. can of SMOKELESS powder cost about $28. My firearms trainer makes flash bang bombs for tactical training and uses only an ounce or so for that, so I would image a pounds worth would make a big boom.
Well, it's a gruesome thought, but perhaps part of the device (e.g., a belt) was still attached to part of the body.
I would think the FBI has seen enough suicide bomber remains, in Iraq, Israel and elsewhere, to know what to look for.
If that's the case, and they're working with the knowledge that he did use the typical suicide bomber MO, the lack of information may be the result of the FBI not being able to make sense of this thing either.
The suicidal person is making a statement -- be it fear, anger, despair, vengeance or the 72-virgin delusion. So what was this kid trying to say by choosing this way to die, at this particular place and time -- if the choice truly was his to make?