  Excited beryllium has been observed to decay into electron-positron pairs
with a $6.8~\sigma$ anomaly. The process is properly explained by a 17 MeV
proto-phobic vector boson. In present work, we consider a family-nonuniversal
$U(1)^{\prime}$ that is populated by a $U(1)^{\prime}$ gauge boson $Z^\prime$
and a scalar field $S$, charged under $U(1)^{\prime}$ and singlet under the
Standard Model (SM) gauge symmetry. The SM chiral fermion and scalar fields are
charged under $U(1)^{\prime}$ and we provide them to satisfy the anomaly-free
conditions. The Cabibbo-Kobayashi-Maskawa (CKM) matrix is reproduced correctly
by higher-dimension Yukawa interactions facilitated by $S$. The vector and
axial-vector current couplings of the $Z^\prime$ boson to the first generation
of fermions do satisfy all the bounds from the various experimental data. The
$Z^\prime$ boson can have kinetic mixing with the hypercharge gauge boson and
$S$ can directly couple to the SM-like Higgs field. The kinetic mixing of
$Z^\prime$ with the hypercharge gauge boson, as we show by a detailed analysis,
generates the observed beryllium anomaly. We find that beryllium anomaly can be
properly explained by a MeV-scale sector with a minimal new field content. The
minimal model we construct forms a framework in which various anomalous SM
decays can be discussed.
