  If the dark matter in the Universe is made of $\mu$eV axion-like particles
(ALPs), then a rich phenomenology can emerge in connection to their stimulated
decay into two photons. We discuss the ALP stimulated decay induced by
electromagnetic radiation from Galactic radio sources. Three signatures, made
by two echoes and one collinear emission, are associated with the decay, and
can be simultaneously detected, offering a unique opportunity for a clear ALP
identification. We derive the formalism associated with such signatures
starting from first principles, and providing the relevant equations to be
applied to study the ALP phenomenology. We then focus on the case of Galactic
pulsars as stimulating sources and derive forecasts for future observations,
which will be complementary to helioscopes and haloscopes results
