  A bulk diluted magnetic semiconductor (Sr,K)(Zn,Mn)$_{2}$As$_{2}$ was
synthesized with decoupled charge and spin doping. It has a hexagonal
CaAl$_{2}$Si$_{2}$-type structure with the (Zn,Mn)$_{2}$As$_{2}$ layer forming
a honeycomb-like network. Magnetization measurements show that the sample
undergoes a ferromagnetic transition with a Curie temperature of 12 K and
\revision{magnetic moment reaches about 1.5 $\mu_{B}$/Mn under $\mu_0H$ = 5 T
and $T$ = 2 K}. Surprisingly, a colossal negative magnetoresistance, defined as
$[\rho(H)-\rho(0)]/\rho(0)$, up to $-$38\% under a low field of $\mu_0H$ = 0.1
T and to $-$99.8\% under $\mu_0H$ = 5 T, was observed at $T$ = 2 K. The
colossal magnetoresistance can be explained based on the Anderson localization
theory.
