Two national tragedies separated by six years and a day - the April 15 bombing at the Boston Marathon and the April 16, 2007, mass shooting at Virginia Tech University - also are notable in marking how technology is reshaping some uses of our freedoms of press and speech.
Six years ago, 32 people were killed in the Virginia Tech rampage by a lone gunman. The incident was marked by an unprecedented call by news organizations for cell phone images and video from the public. Some major newsrooms created special "desks" to receive emails and images from students and others on the scene, even as regular staff scrambled to reach the campus in Blacksburg, Va.
As a result, we received in near-real time, and for the first time in such magnitude, photos and video of armed police running through the campus, of students huddled in locked rooms for safety, and echoes of the last gunshots fired.
Seven years later, citizen camera-phones again came into play along with official video surveillance and news photos and video of the Boston bombing. Joining in the news reporting process was a newer tool - tweeting. As a manhunt for the second bomber went into day two, the combination of networks, online news sites and social-networking offered continuous bursts of text updates, photos and live streams on police activity from hundreds if not thousands of sources.
Even as broadcast pundits provided perspective, tweets gave us street-by-street updates on the search and images from rooftops and backyards of black-clad SWAT teams stalking the remaining suspect.
Still, it was Virginia Tech-plus: More information, more images, in more ways. What is noteworthy from the Boston bombing is how some of that information was used.
Local police eventually sought help from the online community - effectively, from the world - in identifying two suspects, later identified as the bombers: Dzhokhar Tsarnaev, age 19, and his older brother Tamerlan Tsarnaev, age 26. Some credit that tactic with igniting the search effort that led police to the two men.
But even as police were in the early stages of scanning video and still photos for clues to what occurred, what now seems more like online and in-print vigilantism than anything else was gearing up.
The New York Post's front page of April 17 showed a photo of two men watching the race - a pair ultimately never connected to the investigation. The image was published under the screaming headline: "BAG MEN: Feds seek these two pictured at Boston Marathon." The Post later noted that it received the photo and others from the FBI, and pulled it off-line immediately when authorities began to point to others.
On some social-networking sites there was an interactive version of the same unwarranted "blame game": On Reddit, users were shown faces in marathon crowd photos, with added markings that created at least the suspicion of being suspects, sometimes just because those pictured were wearing backpacks. The site focused attention on a missing student from Rhode Island as possibly being connected to the explosions, an erroneous "report" later carried internationally and promulgated on other networking sites like Buzzfeed.
By Friday, Reddit's general manager Erik Martin said he had apologized to the student's family, noting that "crowd-sourced investigation is something that's really new and extreme in this case," he said - and also promised an internal review aimed at preventing such mistakes.
Thankfully, there's been no call for government-imposed regulations or even the oft-used congressional hearing to spank the offending news and social network outlets.
Thus far, criticism of the Post and online abuses has been from journalistic peers. For example, USA TODAY media columnist Rem Rieder slammed Reddit for its "shameful witch hunt that mindlessly smeared the reputations of people guilty of nothing more than attending the Boston Marathon." He also noted Reddit's apology.
A free press must be free to gather and report the news without official restraints, if only to give the public an independent account of how well the authorities respond to such incidents. Such freedom occasionally will invite excess, error, and experimentation that go wrong.
What's important in the aftermath is examining what worked and what did not, and remembering those lessons for what - sadly but inevitably - will be the next round of newsgathering, reporting and the online national conversation about a tragic event that seizes the nation's attention.