This is what the "Uniformen-Markt" from May 1, 1936 says on page 86:
(published also in the magazine "Der SA-Mann", number 15 from 1936):
the SA symbol originated from a 1929-contest, which was lauched by the
SA High-Command. The design was handed over by Hans Zöberlein (the
well-known poet) and the leader from Sturmbann II from Standarte "List"
from Munich, Obersturmbannführer Max Zankl.
The symbol was the old Teutonic sign for lightning together with the so-called
"Mannrune" (the symbol of a stern and unbending man with a flaming sword).
Both symbols were combined with a ring. Later the hook to connect both was
Maybe it was Heck who added the hook, but this is not mentioned!