(WCBS 880) -- This Sunday, over 50,000 runners will tackle the New York City marathon, including retired Marine Micah Herndon who managed to finish the Boston Marathon on his hands and knees, dragging himself to the finish line after his legs gave out.
The video of the 31-year-old from Tallmadge, Ohio has been viewed online over 4 million times.
"The last 4.2 miles it was complete emotional, mental and physical warfare," Herndon told WCBS 880's Marla Diamond.
After his legs gave out, Herndon would not give up. He kept repeating the names of three of his friends killed when a 400-pound IED exploded under the convoy he was leading in Afghanistan in 2010.
"Nothing compares to the pain that they went through and what their families went through," he said.
Marine Mark Juarez and British war journalist Rupert Hamer were killed instantly. Marine Matthew Ballard suffered injuries so painful, he took his own life.
"They put their trust in me and I failed them," he said. "I write their names on my bibs and my wife writes their names on the backside of my hands."
Suffering with PTSD from his tour in Afghanistan, Herndon put a gun to his head in 2013. He found a remedy for his survivor's guilt in running.
"I had my finger on the trigger and their faces popped in my head. Their faces are the ones that stopped me," Herndon said. "I always kept hearing about this runner's high so I tried it out and I actually fell in love with it, mile by mile, step by step."
Although he did not get a qualifying time for the New York City marathon, Herndon got an instant invitation when race officials saw the video of him in Boston.
He hopes his story shows military veterans and others that there is light at the end of the tunnel.