"It leaped up from a couple of feet ahead of me," Keen told Inside Edition, "and grabbed itself onto my arm and pulled me down onto the ground."
Luckily, Tyler Caviness was walking his own dogs nearby and noticed the commotion. He grabbed the dog, which had sank its teeth in Keen's arms and back, by its collar and kept it from going after her. He then called 911.
"The dog attacked the young lady that was running," he tells the dispatcher before putting Keen on the phone.
"I'm bleeding everywhere!" she says. "I was running and a pit bull off its leash jumped right on me and it bit me!"
It turned out the 26-year-old runner, who just recently qualified for the U.S. Olympic trials, needed nearly two dozen stitches to repair the damage.
Keen and Caviness reunited in a moment captured by Inside Edition's cameras. She cried as she offered Caviness a massive hug for what he did that day.
"I heard you're on the mend," he told her.
"Yeah, we're getting there," Keen said. "I've got a lot of stitches."
Still, she hopes to be running again soon.
The dog that attacked her is in city-mandated quarantine.