People from all around the world travel to run the Boston marathon, including more than 250 runners from Arizona who were registered to run.
We spoke to a woman who crossed the finish line a minute before the blasts, along with several other people who participated in the marathon.
Scottsdale runner Lisa Ann Kravetz just completed the Boston Marathon and was looking for her husband when suddenly a major explosion went off that sounded like a cannon.
"I had just come through the finish line, so it was too close for comfort. I came through about in 4 hours and 8 minutes, I had already come through the finish line. I can't even tell you how many feet, less than a quarter mile down from the finish line. I was gathering Gatorade and I was getting my medal and I heard the explosion go off. It was such that I felt it right in my chest, it was that loud. I turned around and saw the smoke billowing... we heard another explosion and at that point everybody in that area, where all the runners come through, corralled in that area, it was mass hysteria. People were all saying 'run!' and it felt like 9/11 revisited."
Lisa, along with her husband and good friend Suzy, are all ok.
Jeff Turner of Phoenix also ran, but finished about an hour ahead of the explosions. He and his two friends say its difficult to see footage of the aftermath. They had just left the area when the blasts occurred.
"How somebody could do something like this, you would never think it would happen at a marathon. Just goes to show you never know," said Turner.
Carl Hove of Mesa had also finished about an hour before the tragedy. He trains with Race Lab.
"I really didn't know anything happened until I started getting all these texts... the more texts I got and the more people asking if I was ok, the more emotional I got," said Hove. "My first response was kind of surreal, like really, a bomb went off? Like, is somebody joking? But when reality set in, the excitement of having a good race today totally went out the window. I can't believe spectators actually died coming to watch us."
We also stopped by Runner's Den in Phoenix, where members of the running community told us they were in shock.
"When you go to these marathons, they're upbeat, they're energetic, you're nothing but positive. You've trained for a year, you're qualified. You don't think there would be a negative spin at the end of it," said Ron French, of Runner's Den.
French says at the end of the race, the crowd is packed in, 5 to 6 people deep -- friends and family all cheering.
"They're there emotionally supporting their loved one, family member, whatever, and for something like this to happen is unbelievable," said French.
"Mentally I'll have to block it out when I'm ready to race, but it's going to be in the back of my mind. Is that car parked along the street? You just won't know anymore. But you can't let it affect you, you just have to go along with your life," said Jim Prescott, who's run the Boston Marathon twice.
Video: FOX 10's Jude LaCava reports.
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