That strange scene - in which Trump turned his table into an al fresco situation room - astounded White House veterans, who were used to presidents retiring to private, secured settings to hash out such an event. Trump became President, in part, because of Democrat Hillary Clinton's neglect of information security. During the 2016 campaign, Trump repeatedly called for Clinton to be jailed for her use of a private email server to handle government business while Secretary of State.
Now, Trump is drawing fire from Democrats for his own seemingly loose attitude toward information security.
He has continued to use an insecure cellphone, according to the New York Times. He may have left a key to classified information on his desk while visitors were in the Oval Office, according to a tweet from a Democratic senator.
And now, Trump has used his bustling club in Palm Beach, Florida, as a "winter White House", except that, unlike the actual White House, the club is full of other people.
Yesterday, Democrats blasted him for his handling of the moment.
"There's no excuse for letting an international crisis play out in front of a bunch of country club members like dinner theatre," Nancy Pelosi, the leader of House Democrats, tweeted.
It is hard to recall any other instance in recent US history when the president seemed to handle an urgent national security matter in a public place as Trump did.
On September 11, 2001, of course, President George W Bush learned of that day's terrorist attacks while he was reading a book to children at a Florida elementary school. Bush continued reading for nearly a half-hour before being whisked away on Air Force One to a secure location.
In Barack Obama's White House, two former aides said, a situation like the North Korean missile test might have been handled similarly: the President would be given a note with the news, then taken to a secure room to discuss a response.
The Mar-a-Lago Club, which Trump has run since 1995, includes tennis and beach facilities for its members and rents its ballroom out for weddings and galas open to non-members.
Trump has an apartment at the club. Club members said that the President seems at ease there, among people who have known him for years - and away from the protests and stresses of his new job. "He's in a safe space," said Mar-a-Lago member Robin Bernstein, an insurance executive.
Membership at the Mar-a-Lago Club now requires a US$200,000 ($278,585) initiation fee - a fee that increased by US$100,000 after Trump was elected.