Graphic Video: Police Taser Man Holding Knife to His Throat Outside Buckingham Palace as Shocked Tourists Watch

British police Tasered a man who was holding a large knife to his throat in front of a crowd of tourists outside Buckingham Palace in London on Sunday.

Scotland Yard said the man, estimated to be in his 50s, acted aggressively when confronted by police outside the palace gates, the Associated Press reported.

Image source: YouTube

Cell phone video posted online showed him holding a green-handled blade to his throat in the middle of the square. Tourists had gathered to watch the palace's changing of the guard event, according to the Daily Mail. A police officer on horseback shouted at passerby to back up and move away.

When an officer first hit the man with the stun gun, he appeared to try to charge toward the officer with his knife outstretched. The man fell to the ground a few moments later, the knife was kicked away and police pounced on top of him.

Image source: YouTube

Image source: YouTube

The man was not immediately named or identified.

Officers said he "tried to make an exhibition of himself during the guard change," according to the Guardian. A police spokesman told the Independent the man was carrying two knives but did not make any threats to the public.

Eyewitness Kevin Burrows told the Huffington Post the man broke through a cordon as the guard change was about to happen.

"I thought 'Oh my God, I can't believe it,'" Brown said. "There must have been about 15 police officers on foot who surrounded him once he'd been Tasered. The police saw him really quickly and were obviously cautious. He was in his 40s I'd say and I think he had knives in both hands. Everybody was standing back when it happened and people were actually quite calm, I think everyone was surprised."

Image source: YouTube

Image source: YouTube

Queen Elizabeth II and her husband Prince Philip were at their country retreat, Sandringham Estate, when the incident occurred.

​Content warning -- graphic video: