DeAgazio's posts - which have since been made private - show the proximity of smartphones to such a sensitive briefing. Photo / Facebook
When Donald Trump entered his private oceanfront club with Japan's Prime Minister Shinzo Abe on Saturday night, it was meant to be a friendly gathering.
It was ultimately a weekend of easygoing bonding first, and strategic affairs second. But then North Korea happened.
The private Mar-A-Lago Club dinner was interrupted after a call to the US President came in, saying Kim Jong-un had just launched an intermediate-range ballistic missile towards Japan.
It was the dictator's most antagonistic move in defiance of international law since Trump was elected.
This left the US President with a breaking security crisis he had to immediately respond to.
Richard DeAgazio, a retired investor who was present at the dinner, six tables away from Trump, snapped pictures of the turn of events and posted them to Facebook.
"HOLY MOLY !!!" DeAgazio wrote. "It was fascinating to watch the flurry of activity at dinner when the news came that North Korea had launched a missile in the direction of Japan. The Prime Minister Abe of Japan huddles with his staff and the President is on the phone with Washington DC. the two world leaders then conferred and then went into another room for hastily arranged press conference. Wow.....the centre of the action!!!"
One of the key security concerns raised in DeAgazio's posts - which have since been made private - is the proximity of smartphones to such a sensitive briefing.
As CNN notes, the patio was only lit with candles and moonlight, and so Trump's aides used the flashlights on their camera phones to help him and Abe read through the documents.
Washington Post reporter Philip Bump said this was highly problematic because smartphones can be used as wiretaps.
"Phones - especially phones with their flashes turned on for improved visibility - are portable television satellite trucks and, if compromised, can be used to get a great deal of information about what's happening nearby, unless precautions are taken," he wrote. A phone flashlight overlooking official documents could have had disastrous consequences if the device was hacked, as the camera would be bearing down straight onto them.
DeAgazio told The Post Mr Trump and Mr Abe left the open terrace and spent 10 minutes speaking in private, before they conducted a joint press conference.
Afterwards, he said, it was back to the event. Trump and First Lady Melania Trump listened to music on the terrace and spoke with other club members.
"There wasn't any panicked look. Most of the people [on the terrace] didn't even realise what was happening," DeAgazio said. "I thought he handled it very calmly, and very presidentially."
In 2013, The New York Times reported on how Edward Snowden insisted that a group of lawyers advising him in Hong Kong "hide their cellphones in the refrigerator of the home where he was staying, to block any eavesdropping".
Leaving them in the fridge would cut out radio signals that could be used to transmit voice data.
DeAgazio's photos show Trump himself using an Android device at the table - a device that could easily be hacked by the wrong people.
Previous reports have suggested Trump's personal phone is old and unsecured.
Earlier this month, University of California computer scientist Nicholas Weaver told NPR his phone "would not meet the security requirements of a teenager", although he admitted he didn't have any first-hand knowledge of its security standards.
Other cybersecurity experts said that if his phone was indeed insecure, it could provide a massive opportunity for hackers to gain access to sensitive information via his phone's camera, microphone and GPS.