Two daredevils climbed to the top of the needle of the Empire State Building on Wednesday and unfurled a large black flag that flapped in the breeze.

One of them appeared to be the stunt artist Angela Nikolau, who posted a P.O.V. video showing a vertiginous view from a narrow platform labeled “Currently at the Empire State Building” on her Instagram account late Wednesday morning.

The message on the flag read, “When the power of love beats the love of power the world knows peace.”

After unfurling the flag, one of the people proposed to the other person, according to a law enforcement officer with knowledge of the matter. Video on CNN shot from high in the air appears to show one of the two people getting down on one knee. Afterward, they hug.

The needle, which houses communications equipment and a very tall antenna, rises about 200 feet above the 102nd floor of the building.

As of 12:30 p.m., there did not appear to be anyone at the top of the building anymore.

Ms. Nikolau is one of the subjects of a 2015 documentary, “Skywalkers: A Love Story,” about Ms. Nikolau and another stunt artist, Ivan Beerkus, who have climbed extremely tall buildings together.

The top of the Empire State Building is not scaled frequently. In 1994, the French climber Alain Robert did so and was promptly arrested.

This is a developing story. Check back for updates.