  We present the package for the simulation of DM (Dark Matter) particles in
fixed target experiments. The most convenient way of this simulation (and the
only possible way in the case of beam-dump) is to simulate it in the framework
of the program for tracing particles in the experimental setup. One of the most
popular such programs is Geant4.
  Specifically, the package includes the processes of DM particles production
via electron and muon bremsstrahlung off nuclei, resonant in-flight positron
annihilation on atomic electrons and gamma to ALP (axion-like particles)
conversion on nuclei. Four types of DM mediator particles are considered:
vector, scalar, pseudoscalar and axial vector.
  In particular, for bremsstrahlung the total cross sections are calculated at
exact tree level (ETL). The code handles both the case of invisible DM mediator
decay and of visible decay into $e^+e^-$ (or into $\gamma \gamma$ in the case
of ALP).
  The software consists of a collection of different classes, inheriting from
the Geant4 framework classes, thus the expected use of this package is to
include it in a Geant4-based code for the simulation of particles propagation
and interaction in the detector.
  As an example of its usage, we discuss the results obtained from the
simulation of a typical active beam-dump experiment, considering $5 \times
10^{12}$ 100 GeV electrons impinging on a lead/plastic scintillator active
thick target, showing the expected sensitivity for the four types of DM
mediator particles mentioned above.
