Donald Trump’s attendance at the NATO Summit has been marked by disagreements between the US President and various EU leaders such as French President Emmanuel Macron. Now, former European Council Chief Donald Tusk seemed to have joined the fray even after the event already ended.

“Despite seasonal turbulences our transatlantic friendship must last #Trump #NATO,” Tusk tweeted a message of unity and cooperation on the social platform on December 5, a day after the 2019 London Summit ended.

While observers found no fault in the message, they are a bit shocked with its accompanying picture. Tusk, who is also an ex-Polish PM, posted a photo showing him pointing his index and middle fingers toward the back of Trump, a gesture that many likened to be that of a gun, according to the New York Post.

With the tweet, Tusk seems to have voluntarily waded into the diplomatic row which started when Canada’s Justin Trudeau and Macron were caught mocking their US counterpart, according to Daily Mail. According to the publication, sharing the photo was “a blatant swipe at the reeling US leader.”

However, political observers were not too surprised with Tusk’s action as he is a known Trump critic and has already crossed swords with the US president when he was still EU Council chief, a post that he held until last week. For instance, he once called Trump’s views as “false and dangerous” in his United Nations speech a few months back.

Germany's Angela Merkel can be seen looking at Tusk’s gesture in the photo. However, it can’t be determined if she reacted positively or negatively to his action.

However, some are a bit concerned about Tusk’s “gun gesture” as it seems to have a threatening undertone. “[Outgoing] European Union Council Leader Donald Tusk tweets himself holding 2 fingers against Trump’s back like a GUN,” user @justathoughtUSA posted on Twitter. “Is that a THREAT?”

“Is this some sort of veiled EU threat aimed at the US?” user @Dispropoganda likewise posted a concerned message on the social media platform.

A few Polish citizens reportedly expressed embarrassment and apologized to Trump on Tusk’s behalf. However, Tusk can’t be reached for comment at the moment.