Probably intended to be read a humor, this light story is probably best called horror. A psychopath in the year 2099 is helping reduce the population of unwanted pets & uncaring pet owners - by shooting both the strays & their owners (strays have id tags identifying owners in this future).
Fact sheet.First published: AntipodeanSF magazine, #114 (November/December 2007).
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Note: Why is this post so short?