I've gotten rid of the original clip from the archive, but there was at least a Southwest arrival into Ontario at the time, and maybe another GA aircraft. Weather like that keeps the Sunday fliers at home here in socal, and Ontario doesn't have the air carrier traffic it once did, or so I'm told.
This happened in the Norton sector at socal, named for Norton AFB, which is now San Bernardino (International, lol) airport. Here's the radar map for the sector, which is mostly a bunch of nonsense lines, but if you know what you're looking for you can find 13 airports depicted. (BNG L35 REI SBD L26 RIV RIR RAL CNO AJO ONT L67 CCB) And yes the northern boundary of Norton is adjacent to High Desert Tracon, E10, or Joshua Approach.
If the pilot had been willing to declare an emergency, the controller could have descended him below the minimum vectoring altitude. Eventually the controller declared an emergency on behalf of the pilot and descended him, and there's a real possibility that may have saved his life.