And then there was President Trump.
London authorities at that point had confirmed only a few details. Shortly after the Drudge tweet, British police again warned against spreading unconfirmed information.
Fifteen minutes later, Trump issued his second tweet since the attack — promoting his administration's legally embattled “travel ban,” which hinders people from several Muslim-majority countries from entering the United States.
As Philip Bump noted for The Washington Post, Trump tends to rush to weigh in on attacks connected to Islamist terrorism but is “remarkably late” in responding to others that are not.
But at that point in the evening (and even by Sunday morning), London authorities had not released any information on the identities, ethnicities or nationalities of the suspects in the attack.
Trump's final tweet of Saturday night was more in line with early statements from other world leaders — a show of unity and support.
One minute after he sent it, British authorities declared the attack to be a terrorist incident.
Overnight, as Americans slept, leaders in Britain and around the world issued statements of condemnation.
On London Mayor Sadiq Khan's Twitter account, which had deferred to police in the early minutes of the attack, the mayor urged “all Londoners to remain calm and vigilant today and in the days ahead” and vowed that terrorists would not cow his city.
On the BBC, Khan also told Londoners to expect a heavy police presence in the days ahead. “No need to be alarmed,” he said. “One of the things the police, all of us, need to do is make sure we're as safe as we possibly can be.”
In Trump's first two tweets of the morning, he attacked political correctness — then quoted a fragment of Khan's statement to essentially upbraid the elected leader of a wounded city.
A spokesman for Khan later responded that the mayor “has more important things to do than respond to Donald Trump's ill-informed tweet that deliberately takes out of context his remarks.”
The president let 15 more minutes go by before he tweeted again. By now, many world leaders had spoken out on the attack. German Chancellor Angela Merkel had joined Britain in “horror and mourning,” and vowed to aid in the fight against terrorism. British Prime Minister Theresa May had laid out details of the attack that had been confirmed, along with her plan to prevent more like it.
At 7:43 a.m., Trump cited the attack to ridicule gun control.
Even as authorities hunted for suspects in Britain on Sunday morning, a spat raged on Internet over whether Trump's tweets had been reckless and offensive or prescient and bold.
The president's critics made much of the NBC Nightly News's refusal to cite Trump's early retweet suggesting the attack was terrorism.
"Translation," CNN host Reza Aslan wrote about NBC's disclaimer: "The president is a man baby that must be ignored in times of crisis."
Noting that Trump had received an intelligence briefing minutes after the attack, the Guardian wondered if whatever he learned influenced his decision to retweet Drudge's speculation. The publication also noted that it was unclear whether the briefing had occurred before Trump's retweet.
Trump-friendly websites, meanwhile, focused on the fact that later that evening, Drudge turned out to be right.
"CNN Host Reza Aslan Calls Trump ‘Piece of S---’ for Correctly Identifying London Terror Attack," Breitbart wrote, for example.
But nearly all of Trump's London tweets drew outrage from someone.
"Political point scoring is the absolute, LAST thing we need right now," a British barrister wrote Saturday, for example — after Trump promoted his executive orders banning visitors from Muslim-majority countries. Even the European Union's top security official called out the president.
And the president's criticism of Khan, London's mayor, instigated a sort of flame war between British and American leaders — with Khan's spokesman and Trump's social-media director sparring as proxies for their bosses.