  We propose that the diphoton resonance signal indicated by the recent LHC
data might also arise from the pair productions of vector-like heavy down-type
quarks with mass around $750$ GeV and above. The vector-like quark decays into
an ordinary light quark and a Standard Model singlet scalar. The subsequent
decay of scalar singlet produces the diphoton excess. Both the vector-like
quark and singlet scalars appear naturally in the $E_6$, and their masses can
be in the TeV scale with a suitable choice of symmetry breaking pattern. The
prediction of such a proposal would be to see an accompanying dijet signal at
the same mass with similar cross section in the $2\gamma + 2j$ final state and
two dijet resonances at the same mass for a $4j$ final state with a cross
section, about 100 times larger. Both predictions can be tested easily as the
luminosity accumulates in the upcoming runs of the LHC.
