evidence: The U.S. Navy SEALs and other troops whose helicopter was shot down in eastern Afghanistan had rushed to the mountainous area to help a U.S. Army Ranger unit that was under fire from insurgents, two U.S. officials said Sunday. [...] Thirty Americans, most of them belonging to the same elite Navy SEALs unit that killed Osama bin Laden, were killed. U.S. officials said. It was the deadliest single loss for American forces in the decade-old war. [...] In that incident, 16 Navy SEALs and Army special operations troops were killed when their craft was shot down while on a mission to rescue four SEALs under attack by the Taliban. Three of the SEALs being rescued were also killed and the fourth wounded.