I'm returning your shovel

Another item from the Glenn Milne rant:
The Mafia-style dirt-covered shovel -- code for digging your own grave -- dumped on Friday at 3.30am on the doorstop of Kathy Jackson, the union official who had the courage to refer Thomson's activities to the police, may as well have been delivered to the Lodge.
Is there any previous instance whatsoever, in fiction or otherwise, of the Mafia using a shovel as a threat? Or of anybody else doing the same? The top 100 entries on google for "shovel, doorstep, mafia" don't happen on an example (other than in the Milne article). "Shovel on doorstep", 2 entries, both recent Australian; :"fish on the doorstep", 17, beginning with The Godfather, and "sleeps with the fishes" lots (despite, apparently, it not being used in those words in The book of the Godfather).
The risk, surely, is that if you're the first person to invent a particular rebus-based threat it may well be misunderstood. Code has to be a recognised convention.

Smear

Correction
The Australian From: The Australian August 29, 2011 9:26AM

THE AUSTRALIAN published today an opinion piece by Glenn Milne which includes assertions about the conduct of the Prime Minister.

The Australian acknowledges these assertions are untrue. The Australian also acknowledges no attempt was made by anyone employed by, or associated with, The Australian to contact the Prime Minister in relation to this matter.

The Australian unreservedly apologises to the Prime Minister and to its readers for the publication of these claims

Well, yes; but I'd say that the Murdochites thought that getting the line "she set up an association later used by her lover to defraud the AWU" into print was worth whatever damages or retractions they get hit with. Not to mention that if she does sue they then get a running story to repeat the line for months. Murdoch thinks we're approaching the endgame, and it's all in.