But the pilot ejected and the other aircraft landed safely, the military said.
Air refueling accident is my guess...
Very likely.
It happened during daylight so the most likely cause was collision during refueling. The KC-130 drags drogues and hoses from just outboard the engines and the receiver aircraft typically flies below the level of the tanker. If the receiver gets to high, the propwash could cause all kinds of undesired effects.