  Exploring the relationship between intriguing physical properties and
structural complexity is a central topic in studying modern functional
materials. Co$_{3}$Sn$_{2}$S$_{2}$, a new discovered kagome-lattice magnetic
Weyl semimetal, has triggered intense interest owing to the intimate coupling
between topological semimetallic states and peculiar magnetic properties.
However, the origins of the magnetic phase separation and spin glass state
below $T_{C}$ in this ordered compound are two unresolved yet important puzzles
in understanding its magnetism. Here, we report the discovery of local symmetry
breaking surprisingly co-emerges with the onset of ferromagnetic order in
Co$_{3}$Sn$_{2}$S$_{2}$, by a combined use of neutron total scattering and half
polarized neutron diffraction. The mismatch of local and average symmetries
occurs below $T_{C}$, indicating that Co$_{3}$Sn$_{2}$S$_{2}$ evolves to an
intrinsically lattice disordered system when the ferromagnetic order is
established. The local symmetry breaking with intrinsic lattice disorder
provides new understandings to the puzzling magnetic properties. Our density
function theory calculation indicates that the local symmetry breaking is
expected to reorient local ferromagnetic moments, unveiling the existence of
the ferromagnetic instability associated with the lattice instability.
Furthermore, DFT calculation unveils that the local symmetry breaking could
affect the Weyl property by breaking mirror plane. Our findings highlight the
fundamentally important role that the local symmetry breaking plays in
advancing our understanding on the magnetic and topological properties in
Co$_{3}$Sn$_{2}$S$_{2}$, which may draw the attention to explore the overlooked
local symmetry breaking in Co$_{3}$Sn$_{2}$S$_{2}$, its derivatives, and more
broadly in other topological Dirac/Weyl semimetals and kagome-lattice magnets.
