  Recently the Telescope Array collaboration reported an observation of cosmic
ray event with very high energy 244 EeV ($2.44 \times 10^{20}$ eV).
Importantly, the event is hard to correlate with the matter distribution in the
local Universe, even after taking into account deflections in magnetic fields.
This implies that the event is likely a nucleus with a large charge. An
attenuation length of the nucleus of such a high energy in intergalactic space
is quite small, therefore its source should be relatively close to our Galaxy.
Using these arguments we derive a new upper bound on a distance to the closest
ultra-high energy cosmic ray (UHECR) source and a lower bound on the UHECR
source number density in general. The distance to the closest source should not
exceed 5 Mpc at 95% C.L. and the 95% C.L. lower-bound on the sources number
density is $\rho > 1.0 \times 10^{-4}$ Mpc$^{-3}$. The number density of UHECR
sources emitting heavy nuclei is constrained for the first time.
