More than 260 people were injured. Three lost their lives as two homemade bombs exploded near the finish line of the Boston Marathon last year.
Austin runner Talaya Frazier was there.
"It's a moment when they say the world stands still, I felt like I couldn't breathe and couldn't feel my heart beating and just...fear," Frazier said.
In 2012, Frazier started a non-profit called CC4C to help raise awareness and money for Austin children with rare and undiagnosed disorders.
Last year, Frazier ran for a boy named Caleb. She snapped a picture of the medal she'd just earned for him and was about to send it his way.
"Right after I shot that, in the background I heard the explosion and saw the smoke but still didn't fathom that's what really had just happened and was kind of stunned. And then all of a sudden I heard the second explosion. That's when I began to panic," she said.
Frazier says since cell phones weren't working well it was hard to reconnect with her teammates.
"Because CC4C had taken a team of 10, a lot of those athletes had their families there so it was just a matter of trying to make sure everybody was accounted for," she said.
This year, Frazier and her teammates will be going back to the Boston Marathon. This will be Frazier's 8th time to run. She and her teammates have no qualms about going...quite the opposite.
She says you can't let the fear of "What if" take away the joy of "What is."
"You appreciate life so much and that's why this year, even going back people say 'Well are you afraid?' I said, 'there's so much meaning behind it, I can't imagine being afraid, 'I just can't wait to come back and see their faces again," she said.
If you'd like more information on Talaya's foundation CC4C and how you can help, click here: www.cc4c.org
This year's race is expected to attract 36,000 runners -- even more than last year -- and 1 million spectators.
Organizers and law enforcement say security will be heightened and they encourage Boston Marathon spectators to leave backpacks and bags at home.