Why is another one from an unspecified plane?

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U.S. military planes collide off Japanese coast; 2 of 7 rescued
Two F/A-18D Hornets approach a Lockheed KC-130J Hercules during an aerial refueling exercise on October 13, 2016.
On Thursday, an F/A-18D Hornet and KC-130J collided off the coast of Japan.
Dec. 5 (UPI) -- Two U.S. military planes crashed in the air during a training mission off Japan's coast Thursday morning with two Marines rescued, the Marines and the Japanese Defense Ministry said.
While refueling in the air, a two-seater F/A-18D Hornet and a KC-130J tanker with five aboard crashed about 200 miles off Iwakuni, Japan, at 2 a.m., the USMC said in a news release.
The Marines first said one service member was rescued alive and several hours later Japanese defense officials reported another person was found.
A crew member in the FA-18 was taken to Marine Corps Air Station Iwakuni and another one from an unspecified plane was taken to a ship of the Japanese Maritime Self-Defense Force.
Japan sent 10 aircraft and the Japan Coast Guard dispatched six patrol ships as part of the rescue operation, government officials said.
Both aircraft, which are manufactured by McDonnell Douglas, left from Marine Corps Air Station Iwakuni, according to USNI News.
The USMC said circumstances of the collision are under investigation.