President Donald Trump ignored the advice of scientists and public health officials around the country — not to mention his own daughter — and looked at the sun without special protective glasses during Monday’s solar eclipse.

Trump, first lady Melania Trump, and son Barron watched the eclipse from the White House’s Blue Room balcony. Although they were all armed with protective glasses, Trump looked up at the sun for a moment, prompting staffers to yell, “Don’t look!”

President Trump sneaks a peek at the #SolarEclipse2017 after taking off his protective glasses pic.twitter.com/sqhhV93LYF — NBC News (@NBCNews) August 21, 2017

Staring at the eclipse is dangerous because the sun has the potential to burn holes in your vision by damaging your retina, as Vox’s Brian Resnick explains. Eclipse glasses are necessary for viewing the eclipse safely because they block all but 0.003 percent of visible light. And because tens of millions of Americans were expected to watch the August 21 eclipse, demand for eclipse glasses sky rocketed. (Amazon was selling a pack of five for $100).

As people geared up for the big event, many shared their excitement — and passed along warnings not to look at the sun without eclipse glasses, including the president’s daughter Ivanka Trump.

So when photos began to circulate of the president looking up into the sun without the glasses, mocking tweets quickly followed, especially since it’s typical for Trump to flout mainstream guidance — including from his own aides:

Scientists: Don't look straight at sun during eclipse.

Trump: Hold my glasses. pic.twitter.com/3MySTJYq4d — Dan Worthington (@danWorthington) August 21, 2017

To be fair, Trump only glanced directly at the sun for a few seconds, which is unlikely to cause any real harm. But the image of Trump choosing to ignore sound advice and stare into the sun, an act that could burn his retinas, is likely seared into some people’s minds.