The Army veteran who fought alongside rebels in Syria, only to be later accused of joining Al Qaeda-linked terrorists by the U.S., has died in Arizona of unknown causes, his family told ABC News. Eric Harroun, 32, succumbed to an "accidental overdose" according to his sister, but an official cause had not yet been released. The Phoenix-born man was first spotted in late 2012 by U.S. intelligence after he appeared in Youtube videos alongside Syrian fighters. In one such video, Harroun was the lone English speaker celebrating amongst rebels who had apparently downed a regime helicopter.