• July 2012: Former New York Police Captain Mistakenly Shoots, Kills Son, after mistaking him for an intruder
• The other day: Retired Chicago cop fatally shoots son after mistaking him for burglar
Both involved legally-owned guns, and obviously very well trained gun owners.
Related: One hell of a list of stats from the The Brady Campaign to Prevent Gun Violence:
A gun in the home is 22 times more likely to be used in a completed or attempted suicide (11x), criminal assault or homicide (7x), or unintentional shooting death or injury (4x) than to be used in a self-defense shooting. (Kellermann, 1998, p. 263).