Among the crowd of 27,000 runners, there were 57 athletes from Hawaii who qualified for the Boston Marathon.
"Everyone wants to run in the Boston Marathon, if you are a runner," said Michael Kasamoto.
Kasamoto finished his eighth Boston Marathon about 20 minutes before the blasts.
"It sounded like two cannons, like the Honolulu Marathon cannons," said Kasamoto.
While finishers heard the explosions and saw smoke, many didn't exactly know what was happening.
"There were some of our friends still on the course. We didn't know whether they were affected. We didn't know what was going on," said Kasamoto.
"When they said it was in the spectator area, it was scary," said Carole Higa. "At that point I started to panic. My husband was in that area waiting for me."
"It's shocking. I kind of in shock, actually," said Angela Sy.
While the blasts happened in Boston, the shock of that event also rattled runners here.
At Runner's Room, Mallory Heller, a marathoner herself, constantly watched for updates on the television as she worked.
"It just made me think of all of my friends, and if any of them were running and it was really scary," said Heller.
Hawaii runners in Boston said they didn't think these blasts would stop them from running this marathon in the future. Other athletes said this event may give them one more thing to worry about on race day.
"After seeing something like this, it makes you more nervous. It's really scary," said marathoner Jessica.
Hawaii runners in Boston are waiting to hear from their friends to find out if everyone from the islands are OK.