Alas, my fellow readers, I have finally figured his riddle out! I know who Scar is!
I shall now provide the evidence.
If you can, look at the tattoo on his arm! His arm people, focus! Seem familiar?
There are several things to point out here. Aside the obvious skin colour and shades, note the clothing. Similar no? That's right. Perhaps not several, so much as few. Having just blown off some poor State Alchemists skull, he rushed over to LA for to take this photo.
There, I rest my case.