Seven marines died last night when their two helicopters collided in a training exercise near Yuma, Ariz., Pentagon officials announced today. The identity of the seven won’t be revealed until next-of-kin have been notified, but they were from the 3rd Marine Airwing based at Miramar in Southern California. There were no survivors of the crash. USA Today has a few more details about the training base in Arizona and the precise location of the accident:

The base website says the base includes approximately 4,000 active duty Marines and sailors. “With access to 2.8 million acres of bombing and aviation training ranges and superb flying weather, MCAS Yuma supports 80 percent of the Corps’ air-to-ground aviation training.” CNN, citing a Marine Corps official, says the aircraft involved were a UH-1 and a AH-1W. …

A military official says the military helicopters crashed in the Chocolate Mountains in southeast California, the Associated Press reports. …

The aircraft collided in a remote portion of the Yuma Training Range Complex. “We’re still gathering a lot of details as the sun comes up,” Lt. Maureen Dooley with the Miramar Air Base in California tells CNN.

Of the four GOP candidates, all of whom were in Arizona last night for the final debate of the primary season, Mitt Romney was the first (and, so far, the only) candidate to respond to the tragedy.

“My heart goes out to the victims and their families of today’s tragic helicopter collision here in Arizona,” Romney said in a release. “Those who serve in our armed forces take risks and face dangers both on and off the battlefield. For defending our country, for volunteering to put themselves in harm’s way, the men and women of our military deserve our most solemn gratitude.”

Echoing Romney, my thoughts and prayers go out to the Marines and their families. What a heartbreaking loss.