In late November 2020, the military-focused website We Are the Mighty posted a story headlined, "Watch this Sentinel destroy a trespasser at the Tomb of the Unknown Soldier."
The story contained a YouTube video showing a hapless tourist stepping beyond barriers and getting close to the tomb, only to be shouted at by one of the guards (known as sentinels).
We see no reason to doubt that the video is real, but it was posted to YouTube in 2016, four years before the story was published.
https://youtu.be/tTqumKNphXM
The Tomb of the Unknown Soldier is an iconic memorial located at Arlington National Cemetery, which has a code of conduct for visitors that emphasizes showing respect. The Tomb contains the remains of fallen American soldiers whose identities are unknown, and it is guarded round the clock by soldiers (sentinels) from the 3rd U.S. Infantry Regiment, also known as The Old Guard.
The incident shown in the video above isn't out of the ordinary. The sentinels are known for responding sharply to visitors who step out of line — so much so that there is a compilation of visitor "fails" on YouTube showing several visitors getting shouted at, along with the occasional disciplined brandishing of an M14 rifle: