President Donald Trump was booed loudly and met with a chant of “lock him up” Sunday night when he was announced as a special guest at Game 5 of the World Series at Nationals Park.

The 45th U.S. president arrived during the first inning as the Houston Astros and Washington Nationals battled to take the series lead. Trump’s arrival was not shown or mentioned on the Fox broadcast. His presence was acknowledged by broadcaster Joe Buck just before the third inning.

Before the fourth inning, however, Trump was greeted by the Nationals’ public address announcer and shown on the stadium’s video screen. The response from the crowd was to boo the president and chant “lock him up.”

MLB commissioner Rob Manfred said Trump decided not to throw out the ceremonial first pitch “in order to make the fan experience as positive as possible” for the series, which was tied at 2 pending the outcome of Sunday’s Game 5. The Astros to a 7-1 win Sunday night and a 3-2 lead.

A presidential appearance at the World Series is nothing new, but in the age of social media and our currently divided political spectrum, a Trump visit wasn’t so simple as a celebrity coming to a game. It was as much a political event as it was at a sports event.