After a pair of explosions rocked the Boston Marathon, killing three and injuring more than 150, millions took to social media to look for loved ones, let friends and family know they were OK, and to express sympathies for victims.
On Facebook, two disparate voices carried the day: the beloved children's TV host Mr. Rogers, who died in 2003, and comedian Patton Oswalt.
A black-and-white photo of a smiling Mr. Rogers made the rounds, with the caption, "When I was a boy and I would see scary things in the news, my mother would say to me, 'Look for the helpers. You will always find people who are helping.'"
Oswalt, a man best known for a wit that can be as merciless as it is acerbic, offered a reminder of the prevalence of good, one that took Rogers' point a step further:
You watch the videos of the carnage and there are people running TOWARDS the destruction to help out… This is a giant planet and we're lucky to live on it but there are prices and penalties incurred for the daily miracle of existence. One of them is, every once in awhile, the wiring of a tiny sliver of the species gets snarled and they're pointed towards darkness. But the vast majority stands against that darkness and, like white blood cells attacking a virus... This is beyond religion or creed or nation. We would not be here if humanity were inherently evil. We'd have eaten ourselves alive long ago. So when you spot violence, or bigotry, or intolerance or fear or just garden-variety misogyny, hatred or ignorance, just look it in the eye and think, "The good outnumber you, and we always will."
In addition to sharing these messages, many on Facebook changed their cover photo to a picture of the Boston skyline, and still others switched out their profile photo for the iconic "B" logo of the Boston Red Sox, or some other similar show of support.
Close to 50,000 Facebook users have joined a "virtual run" event that asks people to "run (or walk) any distance, anywhere and at anytime" to show solidarity in the running community.
NBC correspondent Ann Curry launched a new hashtag #26Acts2, which is an update to #26Acts - a Twitter call to arms for random acts of kindness in the wake of the elementary school shooting in Newtown, Conn.
A piece by Bruce Schneier of The Atlantic in which he implored readers to "Refuse to be terrorized," bore a headline that included the phrase "Keep Calm Carry On." Originally part of a 1939 propaganda campaign in England meant to boost morale, the phrase has of late developed something of a kitsch cool about it, but yesterday and today it was repeated with sincerity time and again on Twitter.
In the moments after the explosions, the Twitterverse was quickly flooded with the hashtag #prayforboston and some variation on the message, "You go to a movie, You get shot, You go to school, You get shot, You go to a marathon, You get bombed."
The terror in Boston also brought out attention-seeking charlatans. Twitter has already suspended a fake account, @_BostonMarathon, which claimed it would donate $1 to victims for each retweet.
But Google offered a stark counterpoint to fake Twitter accounts by establishing a "Person Finder" for the Boston Marathon, a site where people can look for or post information about loved ones. As of Tuesday morning, it was tracking more than 5,200 records.