LONDON (AP) — Police used a stun gun to arrest a man armed with knives outside Buckingham Palace on Sunday as throngs of tourists gathered to watch the Changing of the Guard ceremony there.

Scotland Yard said the man, thought to be in his 50s, was spotted carrying two knives outside the central gate of the London tourist landmark. He did not threaten other people at the scene, but when challenged by police he acted aggressively.