From an AP story by Melissa Goldin headlined “Capitol Police stop a youth performance of the ‘Star-Spangled Banner'”:

Video of a children’s choir singing the national anthem in the U.S. Capitol, only to be unceremoniously cut off by police, spread across social media on Friday.

Capitol Police say singers from Rushingbrook Children’s Choir from Greenville, South Carolina, were stopped May 26 because of a miscommunication. Musical performances in the hallowed seat of Congress require permission, and police said officers had been unaware that the choir had approval from the House speaker. Capitol Police denied choir leaders’ claims that the performance was stopped because it might be found offensive.