We came across this mating pair hovering in a "sun-speck" along the creek-adjacent, woodland trail/road though Mitchell Canyon. To the naked eye it wasn't entirely clear what it was, though I thought I could make out a foamy "nuptial gift" (suggesting a balloon-bearing empidid).
However, I didn't realize it was a mating pair until zooming-in on a photo on the camera display. We observed the two in (roughly) "stationary hover" for over two minutes...don't know how long they were hovering before we noticed them.
After posting this, I noticed @kueda made a very similar observation very nearby about 9 years earlier (with nice accompanying info, and a wonderfully sharp image!)...as did @abmdjoe about 3 weeks earlier here. Seems there's a stable population in the area :-).
A dozen or more individuals scattered over 100 meters
M. Purdy 1392. Photos of two plants within 5 m of one another. Both of these plants collected and will be a part of the same sheet housed at the Inyo National Forest (INF) Herbarium in Bishop, CA.
Population comments: boundary peak (sub)populations not fully explored, but this subpopulation with ca. 50 plants, more observed down and upslope. Population mostly with dehisced fruits; flowers and intact fruits rare. Boechera elkoensis (and possibly 1-2 other Boechera spp: platysperma and paupercula?) also present in this area; B. elkoensis appearing more common than B. pinzliae.