  The propagation of spin waves in magnetically ordered systems has emerged as
a potential means to shuttle quantum information over large distances.
Conventionally, the arrival time of a spin wavepacket at a distance, $d$, is
assumed to be determined by its group velocity, $v_g$. He we report
time-resolved optical measurements of wavepacket propagation in the Kagome
ferromagnet Fe$_3$Sn$_2$ that demonstrate the arrival of spin information at
times significantly less than $d/v_g$. We show that this spin wave "precursor"
originates from the interaction of light with the unusual spectrum of
magnetostatic modes in Fe$_3$Sn$_2$. Related effects may have far-reaching
consequences toward realizing long-range, ultrafast spin wave transport in both
ferromagnetic and antiferromagnetic systems.
