It appears a U.S. MH-47 special operations variant Army National Guard CH-47 Chinook was brought down by hostile fire in Afghanistan. While information is scarce about the crash western sources are saying it was likely shot down. The Taliban say they hit the chopper carrying U.S. special operators with a rocket following a "heavy" raid. While it's too early to tell for sure, I'd guess the helo was hit with an RPG since MH-47s are equipped with advanced infrared countermeasures designed to foil heat-seeking shoulder-launched missiles. It turnd out, the chopper was indeed downed by a rocket propelled grenade. Decades after its first appearances on the battlefield, the relatively-low tech RPG remains one of the biggest surface-to-air threats to helicopters.
A CH-47 Chinook was shot down in July by insurgents using an RPG. That incident left two soldiers wounded.
Our thoughts are with the families of those on board the MH-47.