I'm not an expert on suicides, but I just bet that the statistics would show that bombing oneself as a way of suicide (other than terrorists) is rare....and THAT has to be the biggest understatement of the century.
I can't recall EVER hearing of someone in the US building a bomb and blowing themselves up to commit suicide (intentionally as opposed to accidentally). Not saying it's never happened, just that I can't recall a case of it, ever. If it turns out that he did try (3 times) to access the stadium, and had more bomb-materials, jihadist materials and mosque connections, the only reasonable inference would be that he's a jihadist suicide bomber.
Sure hope this investigation doesn't go the way of the OKC investigation, where the FBI quickly shut down (due to Jamie Gorelicker or someone higher?!) all avenues of investigation except Tim McVeigh/Terry Nichols.
So rare that a report from CDC MMWR report about suicides amongst 14-19 year old ( I hope that is the right age group) from a few years back does not even mention it as a method.