BRUTAL MURDER. -- The Dublin Packet of Tuesday, announces the inhuman murder of a man named Sherlock, holding, in conjunction with his brother, 200 acres at Croalstown, a few miles from Trim, in the Athboy district.  This man came to Navan to consult Dr. BYRON on the case of his wife, who was extremely ill.  The doctor being absent on a medical call, the poor man waited his return.  The doctor gave his advice, and the man having procured the medicine ordered, proceeded home.  On his way beyond the village of Dunderry-bridge (a short distance) he was way-laid and fired at.  The shot took fatal effect, and the victim survived only a few hours.  It appears that the deceased complained of being cold, got off his car, when a man came up and shot him.  Had he been fired at on the car, it is probable two lives would have been sacrificed.  Ribbonism has spread to a fearful extent in this country.  The reason alleged for shooting SHERLOCK is for dispossessing some tenants on the estate of Lord TRIMBLESTOWN.