You would probably be better off using the entityCreating event.

Example (this wasn’t tested or done in a proper editor so be weary):

local policeStations = {
    vector3(425.36, -982.03, 30.71),
}
AddEventHandler("entityCreating", function (entityHandle)
    local coords = GetEntityCoords(entityHandle)
    for i = 1, #policeStations do
        local station = policeStations[i]
        if #(station - coords) < 50.0 then
             -- canceling the event will cause the entity to not be created for other
             -- clients and be removed from the calling client, we return here to not
             -- keep doing the loop.
             return CancelEvent()
        end
    end
end)