Bruce Maxwell faced the flag, put his hand over his heart and took a knee when the national anthem began to play.

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Maxwell, the Oakland A’s rookie catcher, became the first Major League Baseball player to kneel before a game, doing so Saturday in the wake of President Donald Trump’s comments about players peacefully protesting during games.

“Don't be surprised if you start seeing athletes kneeling in other sports now,” Maxwell tweeted, foreshadowing his own actions. “Comments like that coming from our president. WOW! Inequality is being displayed bigger than ever right now as our president shows that freedom of protest and speech is not allowed. This now has gone from just a Black Lives Matter topic to just complete inequality of any man or woman that wants to stand for their rights.”

Maxwell was hit with a foul ball Wednesday and was not in the lineup Saturday because of the league’s concussion protocol. The team said it supports Maxwell’s decision.

"The Oakland A's pride ourselves on being inclusive," the team said on Twitter. "We respect and support all our players' constitutional rights and freedom of expression."

Maxwell, the son of a military family, took to social media earlier in the day after Trump’s comments that NFL players who kneel in protest should be off the field and fired. Trump also took aim at the NBA when he rescinded an invitation to the White House to Golden State Warriors star Stephen Curry and the team for winning the league’s championship.

Maxwell, who is black, was born in Wiedbaden, Germany, when his father was stationed there with the Army. Maxwell started his protest in opposition to Trump and to show solidarity with NFL players who have taken a knee during the national anthem.

"Bruce has made it clear that he is taking a stand about what he perceives as racial injustices in this country, and his personal disappointment with President Trump's response to a number of professional athletes' totally peaceful, non-violent protests," Matt Sosnick, Maxwell's agent, told the San Francisco Chronicle. "Bruce has shared with both me and his teammates that his feelings have nothing to do with a lack of patriotism or a hatred of any man, but rather everything to do with equality for men, women and children regardless of race or religion."