  Using the standard Hamiltonian approach followed by ADM formalism to the
geometry of a Schwarzschild black hole, we show that the interior spacetime of
Schwarzschild black hole behaves like a relativistic free particle with Planck
mass $M_{p}$. We further present the (anti-)BRST quantization of the
relativistic free particle representing the interior of Schwarzschild black
hole. With help of the (anti-)BRST formalism, we determine the physical states
of the system in general Hilbert space. This is a novel observation in the
context of gauge theoretic approach to gravity.
