Automorphisms of the Cameron's monster with parameters $(6138, 1197, 156, 252)$

Let the $3$-$(V, K, \Lambda)$ scheme $E=(X,B)$ be an extension of the symmetric 2-scheme. Then either $E$ is Hadamard $3$-$(4\Lambda + 4, 2\Lambda + 2,\Lambda)$ scheme, or $V = (\Lambda + 1)(\Lambda^2 + 5\Lambda + 5)$ and $K = (\Lambda + 1)(\Lambda + 2)$, or $V = 496$, $K = 40$ and $\Lambda = 3$. The complementary graph of a block graph of $3$-$(496,40,3)$ scheme is strongly regular with parameters $(6138,1197,156,252).$ Let's call this complementary graph Cameron's monster. In this paper automorphisms of monster are studied.