It wasn't on the note. He evidently wrote "Ismail Ax" (not Ishmael X) on his arm with red ink.
Perhaps there is another explanation for “Ismail Ax” —
M. E. H. Ismail, The zeros of basic Bessel functions the functions J+ax (x) and the associated orthogonal polynomials, J. Math. Anal. Appl. 86 (1982), 1-19.
http://islamthreat.blogspot.com/2007/04/cho-seung-hui-was-inspired-by-islam.html
This link makes an Islamic tie to “Ismael Ax”.
Very early, we’ll see.