Here's my concerns in two sentences: This was a professional, ME terrorist-caliber bombing supposedly done by a complete amateur bomber. Although it's certainly not impossible, that doesn't quite add up based on what we know now.
Well, we don't know what kind of ordnance was used, yet. Once the authorities release that information, we can speculate more. However, I wouldn't think a very bright engineering student from a very bright background would find it difficult to create an explosive. The terrorists are surely the most barbaric minds on earth, but they manage to create these things.
And this is based on what exactly, besides wishful thinking?
One does not need to have won a Nobel Prize to blow oneself up.