  The paper contains a rigorous proof of existence of symbolic dynamics chaos
in the generalized H\'enon map's 4th iterate $H^4$, which was conjectured in
the paper \textit{A 3D Smale Horseshoe in a Hyperchaotic Discrete-Time System}
of Li and Yang, 2007. We prove also the uniform hyperbolicity of the invariant
set with symbolic dynamics. The proofs are computer-assisted with the use of
C++ library \textit{CAPD} for interval arithmetic, differentiation and
integration.
