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MIAMI (CBSMiami) – Hopefully you weren’t surprised when you got an alert from President Donald Trump on your cell phone this afternoon.

It’s the first ever test of a national presidential alert system that will let any president issue a warning about a crisis. That could include a missile launched by another country at the US or a tsunami.

“When those messages appear on mobile devices, people should take those extremely seriously, it has some direct impact on either life or safety,” said FEMA’s Antwane Johnson.

Johnson is in charge of the agency’s public alert warning system that will send out the nationwide test of the presidential alert.

“if we have something that’s of national significance, we can rapidly notify the American public of that event,” he said.

Government agencies nationwide have issued more than 40-thousand emergency alerts to cell phones since 2012. But those Amber and weather alerts target specific regions, this new presidential alert will be nationwide and only used for advance warning of national crises.

“It should be reserved for true situations, true emergencies when we need to get the public’s attention,” said former Secretary of Homeland Security Jeh Johnson.

Johnson said it is designed to be used very specifically and rarely.

“This is something that should not be used for a political agenda,” he said.

Johnson said that’s especially important because no one can opt out of these alerts.

“One thing that we need make very clear is that there are laws, policies, and procedures that are in place other protocols to assure the system is used in accordance with its intended use as defined by the law,” said Johnson.

Alerts are not foolproof, however. In January, Hawaii’s emergency management agency mistakenly sent out an alert warning of a ballistic missile threat to more than a million cell phones.

Mistakes like that could make people nervous about this new nationwide alert. Andy Whitehouse teaches Communications at Columbia University.

“The fact that you can’t turn this alert off, that it will be something that will arrive on your phone whether you like it or not I think was probably upsetting and concerning to some people,” said Whitehouse.

The test was scheduled for 2:18 p.m. It set off the same loud sound used for other alerts.