A retired Marine and double amputee is competing in a running challenge like no other.
Combat engineer Rob Jones is determined to run 31 marathons in 31 different cities in 31 consecutive days to support disabled veterans.
Jones lost both of his legs when he stepped on an improvised explosive device in Afghanistan.
A crowd of supporters gathered in Boston early Sunday morning to watch Jones run the fourth marathon of his series.
This is not Jones' first incredible challenge he has undertaken. He also won the bronze medal in the Paralympic Games in 2012, and he is the first and only double amputee to bicycle more than 500 miles across the country.
Jones hopes his actions will bring awareness to the challenges veterans face.
"People come back and struggle with what they experience, and there's nothing wrong with that," Jones said.
"I just want to make sure both sides of the coin are being seen," Jones said. "There are the people that are struggling and we will help them; but there's also this group over here that are doing fine, and both groups can contribute to society."
His final marathon will end in Washington, DC, on Veteran's Day.