I think I have to go with #2 on this one, with a smart dog, you can train it to do just about anything, and this isn't the 1st time I've heard of this happening. This happened in Charleston SC when I was stationed there, in the late 80's. I hope they catch this person, and that the lady is alright, also that they don't put these dogs down, for doing what they were told and trained to do.
Cheers Quad
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RIP Megan 3/1998-5/28/2013