A feud between journalists broke out on social media after Jon Karl of ABC News posted a photograph from the White House and pointedly commented on Fox News' John Roberts not wearing a mask.

Karl posted the photo to his social media account on Monday during a White House media briefing.

"Almost everybody in the Rose Garden is wearing a mask — almost everybody," he tweeted.

Many on social media took him to task for the tweet because it showed only two people without a mask to stop the spread of coronavirus — President Donald Trump and reporter John Roberts.

Roberts fired back to explain why he wasn't wearing a mask but still respecting social distancing guidelines.

"Facts - I was quietly seated more than 6' away from the closest person (adhering to CDC social distancing guidelines) -When the press conference began, I put mask on," Roberts tweeted.

"So - what, exactly is the basis for this petty effort at shaming????" he asked.

Others on social media pointed out evidence that Roberts was wearing a mask at other times, while some posted photos of Jon Karl neglecting to wear a mask a taco shop for Cinco De Mayo.

Karl tweeted on Tuesday that his tweet had left the wrong impression.

"Yesterday I tweeted photos of the extraordinary scene in the Rose Garden. The photo of @johnrobertsfox left the wrong impression," Karl said.

"He is a good reporter who cares about protecting his colleagues and his family. He was practicing social distancing. I did not mean to imply otherwise," he added.

Here's the latest on guidelines about mask guidelines:

WATCH: Dr. Anthony Fauci recommends wearing masks 'for the time being'www.youtube.com