Seattle runner Kelly Herron has a clear message after defending herself from an attacker hiding along her route: Keep fighting.

The 36-year-old marathoner-in-training was four miles into her run in Seattle’s Golden Gardens Park last week when she stopped to use a public restroom. Police say Gary Steiner, 40, a registered sex offender in Arizona, was hiding in the bathroom and attacked her.

Herron had taken a self-defense workshop three weeks before the incident. While many victims of assault or attempted assault don’t or can’t fight back, Herron decided to use everything she had learned in that class to fend off her attacker as he pinned her down on the floor of a bathroom stall.

“I fought for my life screaming (”Not today, M**F**er!”), clawing his face, punching back, and desperately trying to escape his grip - never giving up,” Herron wrote in an Instagram post that had been liked more than 19,000 times as of Monday morning.

She said she was able to escape and locked the man in the bathroom until police arrived. Herron told ABC News that “Not today, motherf****r” became her “battle cry” as she defended herself.

“I learned put hard bones in soft, fleshy areas,” she said of the workshop she attended.

Herron described being attacked while training as “her biggest running nightmare,” a sentiment many women who exercise alone can relate to. A recent survey by Runner’s World found that 43 percent of women sometimes experience harassment while running, compared to 4 percent of men.

Last summer, the deaths of three women in nine days heightened anxieties within runners’ communities, as all three victims were out jogging at the time they went missing.

Steiner has been charged with attempted second-degree rape and second-degree assault with sexual motivation.

Herron wants people to know they should never stop fighting or stop running.

“I couldn’t remain the silent, anonymous victim - there is a message of survival that is too important to remain untold,” she wrote in another Instagram post.