UPDATE: Steve was carried out of Trump Tower on a stretcher.
UPDATE: The AP reports that Steve made it to the 21st floor of the 58-story building. He started climbing the building from a terrace shortly after 4 p.m. and is now in police custody. Donald Trump, who lives in Trump Tower, was not in the building at the time.
UPDATE: Steve the Climber has been pulled into the building by police.
UPDATE: A video titled "Message to Mr. Trump (why I climbed your tower)," featuring a man who resembles "Steve," has surfaced on YouTube. In it, he says he's an "independent researcher" hoping to speak with Trump. He also ends it with a message to vote for the Republican presidential nominee in November: