Was looking up Qs reference to ELF on a Shelf – probably a nothing burger in regards to the post, but I found some interesting articles….
MKULTRA - Classic
https://heavy.com/news/2013/09/washington-navy-yard-shooting-conspiracy-theories-aaron-alexis/
https://en.wikipedia.org/wiki/Washington_Navy_Yard_shooting
Before the shooting, Alexis sawed off the shotgun and scratched the phrases "Better off this way!", "My ELF weapon!", "Not what yall say!", and "End to the torment!" onto the gun's receiver
ELF in this case = Extremely Low Frequency
POSYDON – found this interesting because of the geometrics and Australia – lots of info here
http://www.bldgblog.com/tag/elf/
https://www.maritime-executive.com/article/russia-readies-underwater-monitoring-system