Why is my cat purring one minute then trying to kill me the next?

[retainertrainer]

What goes through her head? She'll come up to me for a fuss,I'll gently stroke her,she purrs-this goes on for a couple of minutes and then she'll suddenly flip out on me,clench my hand in her jaws and do that rabbit kick thing with her back legs. It really hurts! She really means it! I have to get her by the scruff to get her off me.

For background she's a rescue cat,2 years old,found in a log shed as a baby. Her mum was lovely,very placid. I'm guessing this is her feral fathers side!

My late great aunt had a friend who had a fair to middling evil tom cat. Said tomcat was squaring off to another local tom through the window and great aunt's friend tried to interrupt the awful sounds and pick her cat up from the windowsill.

Great aunt's friend was a frail 70 yr old and honestly and genuinely needed hospital treatment. The tom had been on high alert and completely focused on the rival. When he was unexpectedly touched he reacted as any large, vicious, overstimulated tom would and kicked his owner's arm to shreds. Poor woman needed stitches and lots of antibiotics.

I never met the evil creature, but heard all about him as he was a legend in the village.