Seventeen Menlo Park residents, five from Portola Valley, two from Woodside and one Atherton resident were among the nearly 27,000 runners registered for the Boston Marathon, according to the official 2013 registration site.
CNN posted that two bombs killed three people and injured at least 180 after exploding near the finish line about two hours after the first wave of runners had completed the race on April 15. The dead included an 8-year-old boy there to watch his father run; his mother and sister were badly hurt by the explosions.
Facebook employee and dedicated runner Jessica Shambora described how a "beautiful day" turned terrible in a blog post. After crossing the finish line, she went to pick up her bag when the bombs exploded. "Most of the runners were in a post-race daze, cold and stumbling around and suddenly terrified," she wrote.
She found her boyfriend and a group of friends, then returned to where they were staying in Cambridge.
"I am still in shock and not sure I have much to add at this point. Just want to let you know and share my sadness. Despite the tragedy I will still try to remember this as a day of great courage, from the runners to the first responders," Ms. Shambora wrote.
She told the Almanac that she and her boyfriend ran the marathon "because we are runners. We both qualified over the past year and a half and of course Boston is a big goal for many runners."
Google created a "people finder" website to help connect those concerned about marathoners with status updates for approximately 48 hours after the bombings. The website functioned like a bulletin board an update on someone's condition appears only if another person has contributed information, so if a name does not display any results, it does not indicate anything about that person's condition. The site had updates on five Menlo Park runners which indicated they were alive as of Tuesday evening.
One registrant -- Arnaud Mauvais -- alerted friends via Twitter that he wasn't in Boston: "(I'm) not running the marathon; changed plans."
If you have a name along with a phone number or home address, you can check for updates on the Red Cross site.
On Monday night President Barack Obama addressed the nation. "We still do not know who did this or why. And people shouldn't jump to conclusions before we have all the facts. But make no mistake -- we will get to the bottom of this," he said. "And we will find out who did this; we'll find out why they did this. Any responsible individuals, any responsible groups will feel the full weight of justice."
On Tuesday morning FBI investigators said they had no suspects yet, but were continuing to carry out searches and question witnesses. Initial reports suggest that one bomb may have been placed in a trash can near the finish line, converting the metal into shrapnel as it exploded.