Caitlin Keen explained the attack, saying the dog "jumped on my back, took a piece out of the top of my back...I knew it was trying to kill me, but I was going to fight back."
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The pitbull mix jumped on Keen as she trained at Trinity Trails in Fort Worth.
Graphic pictures show the puncture wounds to her body.
She got away when another runner helped fight the dog off with a stick.
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"Before I knew it, the dog had jumped up on me, grabbed my arm, pulled me to the ground," Keen said. "I got up and tried to sprint away. Grabbed me by the back, pulled me back down."
The dog is in quarantine.
The owner was found and is trying to get it back, but it's not clear yet of the animal will be put down.