Jacksonville has become a huge running community over the years, being home to the nation's largest 15K -- the annual Gate River Run.
There's no doubt many of those runners who call Jacksonville home have to be shaken by the explosions at the Boston Marathon on Monday.
Doug Alred, race director for the Gate River Run, said a number of local runners participated in the Boston Marathon, but he said those he knew who were running were safe.
Runners around the River City shared their reactions about what happened:
"It's pretty scary, isn't it? You may not want to be at a major event like that," runner Laura Wesson said. "But those runners, they're probably going to go anyway because they're dedicated."
"It's so unexpected. I mean, I would never think an explosion at a marathon," runner Morgan Scovill said. "It's so sad. My prayer is all to them."
"For something that's supposed to be so much fun and energetic and helping everyone, and like you said, it's not safe," runner Beverley Sue said. "What is safe now?"
"It's such a scary thing to have happen on a day like the Boston Marathon, where they know they're going to have a huge crowd," said one local runner who worked for the Department of Homeland Security. "No matter what sort of security measures we take, there's always some crazy idiot out there."
Todd Williams, a five-time Gate River Run champion, said an explosion at a race is the last thing on a runner's mind.
"At the 4:09-, 4:10-minute mark in a major marathon, that's really the time that the majority of the people are coming across and trying to break that four-hour barrier," Williams said. "My thinking was, I mean, whoever is responsible definitely knew what was going on within the race situation."
For anyone trying to locate a runner in the Boston Maraton, click here.