As Marine veteran Micah Herndon dropped to his knees and began crawling in Monday's Boston Marathon, three names kept repeating in his head as he fought through the pain to cross the finish line.

Mark Juarez. Matthew Ballard. Rupert Hamer.

Juarez and Ballard were good friends and fellow Marines who were killed in 2010 along with Hamer, a British journalist with Herndon's division.

The three were in the same vehicle when it was destroyed by an improvised explosive device during a mission in Marjah, Afghanistan.

Herndon, 31, had their last names on the laces of his running shoes on Monday, using their memory to help drag himself across the finish line after three hours and 38 minutes.

"I run in honor of them," Herndon told Ohio's Record-Courier. "They are not here anymore. I am here, and I am able. I am lucky to still have all my limbs. I can still be active. I find fuel in the simple idea that I can run."

The Ohio native had never run a full marathon until this year, and his time in his first race qualified him for the Boston Marathon, according to the Record-Courier. He often repeats the names "Juarez, Ballard, Hamer" out loud as he is running.

Those names have given him power. When his body stopped on Monday, they kept him going.

"If I get a heat cramp while running or my feet hurt or I am getting exhausted, I just keep saying their names out loud to myself,'' he told the Record-Courier. "They went through much worse, so I run for them and their families."