Sunday was Trump's first appearance as president at a Major League Baseball game.

Posted on October 28, 2019, at 9:29 a.m. ET

Donald Trump was loudly booed by the crowd at Nationals Park in Washington, DC, Sunday during his first appearance as president at a Major League Baseball game.

The crowd also chanted "lock him up!"

The Nationals Park crowd loudly booed President Trump after he was introduced. An inning later, some fans chanted, “Lock him up! Lock him up!” 

Game 5 of the World Series is the first MLB game that Trump has attended as president.

The Nationals Park crowd loudly booed President Trump after he was introduced. An inning later, some fans chanted, “Lock him up! Lock him up!” Game 5 of the World Series is the first MLB game that Trump has attended as president.

Trump, along with First Lady Melania Trump and some GOP lawmakers, attended Game 5 of the World Series hours after he announced the death of ISIS leader Abu Bakr al-Baghdadi during a US raid in Syria.

At the end of the third inning during the Houston Astros–Washington Nationals game, the crowd cheered as the Jumbotron paid tribute to US service members.

The crowd's cheers immediately turned to resounding boos heard all around the ballpark when the announcer introduced Trump and the Jumbotron showed the president standing and clapping.

Trump continued to smile and clap.

WATCH: President Trump met with loud boos as he is introduced at the World Series in Nationals Park on Sunday night.

WATCH: President Trump met with loud boos as he is introduced at the World Series in Nationals Park on Sunday night.

Some sections of the crowd then began chanting "lock him up!"

President Trump was booed loudly by the fans at Nats Park when he was shown on the big screen. 
Then came a loud chant: “Lock him up.” @wusa9

President Trump was booed loudly by the fans at Nats Park when he was shown on the big screen. Then came a loud chant: “Lock him up.” @wusa9

My wife sends along this video of crowd chanting “lock him up” as POTUS introduced at World Series.

My wife sends along this video of crowd chanting “lock him up” as POTUS introduced at World Series.

A couple of "impeach Trump" signs were also seen in the stadium.

Another sign seen at the game said "veterans for impeachment."

A White House spokesperson did not immediately return a request for comment. As of Monday morning, Trump has not tweeted about the game.