It was at 2:49 p.m. EDT when two homemade bombs - separated by 14 seconds - killed three people and injured more than 250 others near the finish line of the Boston Marathon.
Several dozen area runners participated in that event, and they recall the confusing, chaotic moments immediately after the bombs.
Connie Shaner: I was walking to my hotel near the Boston Commons and heard the explosions and just assumed it was cannons going off for celebration of Patriots' Day.
Mike Marty: A volunteer near us said he'd heard a transformer blew. That's the first I heard.
Amy Perez: I heard explosions and screams, but there was nothing malicious in my mind. I thought it was thunder, even though, honestly, there wasn't a cloud in the sky. You're a little disoriented after a marathon anyway, so nothing really makes sense.
Robin Krueger Romero: I thought maybe they were imploding a building or something, which is really weird for a holiday, but that's what I thought it was because nobody really knew.
Dorothy Neider: My first thought was, 'That didn't happen when I crossed the line.' I turned to (friend) Kerri (Coady) and said, 'Is that normal?' And she just had this look in her eyes. She had been to Boston before and she said, 'No.' Then my mind started racing. I thought, 'Did the stands fall down? Could it have been a bomb?' I didn't know.
Kerri Coady: We both thought maybe it was fireworks or something, which wouldn't make a whole lot of sense. We definitely heard it and then we heard the second one and saw police going in and people coming out, so we just tried to get out of there.
Perez: People were scurrying us away, they were trying really hard to get us out of the intersection. I thought that was because there were a lot of us and they wanted to keep us moving.
Neider: We started walking around. Within a few minutes we saw cops running down the street, and they were like 'Move out of the way!'
Coady: It was sort of a slow start, then it gained momentum quickly. First we saw three or four policemen heading toward the finish line. They looked very serious and it seemed like something big was going on. I'd say within a few minutes that escalated. As the runners who just finished or who were closer to the finish line than us, we could see that some of them were crying and were just physically shaken.
Neider: Slowly you just saw signs of chaos erupting. It was crazy. You saw ambulances and police cars and people were bawling and flipping out. My thought was that I had to find my husband and kids.
Shaner: I physically walked into my room and my husband had left the TV on and it was right there on the widescreen TV - the finish line and nobody was finishing.
Neider: We walked to a corner and a reporter told us what was going on. He heard some chatter because he had a walkie-talkie and he said there might have been two bombs and there might have been some casualties.
Douglas Weddell: I was in my hotel room, which was about a block and a half from the finish line. I heard a lot of sirens and my phone just started going nuts with all the text messages that had been sent.
Chad Raymo: My sister called and I assumed she was congratulating me on finishing the marathon. The first question was, 'Where were you when the bombs went off?' I looked around and said 'I have no idea what you are talking about.' Right on cue, people at the front desk changed all the local TVs to the local news stations. All of the sudden you see this disaster.
Ilma Calite: I turned on my cell and then I had, like, five missed calls and messages and all these text messages, I was like, OK, I know I just ran the Boston Marathon but I'm not that popular.
Scott Spillman: I was making my way back to where I was staying in Cambridge. I had a text from a friend who worked at a shop in Boylston, right near the finish, telling me not to come back toward the finish because bombs had gone off. That was pretty creepy because that was the only information I had. So I called my parents who were at home and asked them to check and see if there was any coverage or anything about it. Sure enough, it was starting to be shown on TV. But they knew I was OK.
Weddell: It was just this complete change from a celebration to a war zone with areas cordoned off, soldiers, policemen, ambulances. It was just a huge contrast. Obviously Bostonians were somewhat shocked. People were walking around in sort of a daze. . At the same time, you had this great feeling of people trying to help each other. Restaurants were offering free meals to investigators or National Guardsmen who came through the door. Everyone really pulled together to try to make the best of the situation.