secure communications...they should have known beforehand that "Signal" was inappropriate for sharing such confidential material...they, like the Captain of a ship that collides with another ship (see "USS Truman"), must be held accountable...and be Replaced...with others who have the experience and demonstrated performance.
To not replace them just invites even more such serious errors.
While the 'Signal' app has been used for several years, knowledgeable users have always understood that it is not to be used for transmitting classified information....see the following excerpt from the attached article...
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Government officials have used Signal for organizational correspondence, such as scheduling sensitive meetings, but in the Biden administration, people who had permission to download it on their White House-issued phones were instructed to use the app sparingly, according to a former national security official who served in the administration.
The official, who requested anonymity to speak about methods used to share sensitive information, said Signal was most commonly used to notify someone that they should check for a classified message sent through other means.
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Link: https://apnews.com/article/signal-app-atlantic-war-plans-32699da142c5209b845e57f690df4925