  The space and time configurations of the dissociation of $^8$He into
$^6$He+$n$+$n$, on C and Pb targets, have been explored simultaneously for the
first time. The final-state interactions in the $n$-$n$ and $^6$He-$n$ channels
are successfully described within a model that considers independent emission
of neutrons from a Gaussian volume with a given lifetime. The dissociation on C
target exhibits a dominant sequential decay through the ground state of $^7$He,
consistent with neutrons being emitted from a Gaussian volume of
$r_{nn}^{\rm{rms}}=7.3\pm0.6$~fm with a $n$-$n$ delay in the sequential channel
of $1400\pm400$~fm/$c$, in agreement with the lifetime of $^7$He. The
lower-statistics data on Pb target correspond mainly to direct breakup, and are
well described using the $n$-$n$ volume measured, without any $n$-$n$ delay.
The validity of the phenomenological model used is discussed.
