This relates to the same accident as the thread "Bell 407 Crash in Hawaii" started by KiwiNedNZ on 9 June 2022 with most recent post by SASless on 24 June 2022. By that time in that thread it had been reported the tail boom had separated and one attachment bolt was missing. But prompted by the comment by SASless above (#2) and the photo of the tail boom (#1), I started to look for more info on this case, for example:
https://www.westhawaiitoday.com/2022...-before-crash/
It was the upper left attachment bolt that was missing and apparently lower left bolt was showing signs of fatigue. But aside from the upper left bolt the remaining three were still in place. So it appears that having only one bolt fail is enough to cause such a catastrophic failure of the entire structure. As SASless has already implied, this would be a complete lack of redundancy.
Note that both the upper left and lower left attachment bolts would be those that are predominantly in additional tension (beyond the initial pretensioning) due to the tail rotor torque reaction. So if any of the bolts would have failed due to fatigue, those two were the most likely to go first.
While reading material related to 407 boom attachment, I also noticed initial manufacture and maintenance manuals for the 407 had the bolts tensioned (torqued) to beyond their recommended range. That probably had no influence (in the meantime) on this crash, but it is a worry that this could have happened to such a safety critical attachment. Reminds me of the other case I read here of the Bell 212 which crashed as it was fitted with pins attaching main rotors that had been manufactured using the wrong type of steel (from a Bell subcontractor) and which failed as a consequence, killing the pilot.