  To comprehend the recent Brookhaven National Laboratory experiment E788 on
$^4_\Lambda$He, we have outlined a simple theoretical framework, based on the
independent-particle shell model, for the one-nucleon-induced nonmesonic weak
decay spectra. Basically, the shapes of all the spectra are tailored by the
kinematics of the corresponding phase space, depending very weakly on the
dynamics, which is gauged here by the one-meson-exchange-potential. In spite of
the straightforwardness of the approach a good agreement with data is acheived.
This might be an indication that the final-state-interactions and the
two-nucleon induced processes are not very important in the decay of this
hypernucleus. We have also found that the $\pi+K$ exchange potential with soft
vertex-form-factor cutoffs $(\Lambda_\pi \approx 0.7$ GeV, $\Lambda_K \approx
0.9$ GeV), is able to account simultaneously for the available experimental
data related to $\Gamma_p$ and $\Gamma_n$ for $^4_\Lambda$H, $^4_\Lambda$He,
and $^5_\Lambda$He.
