"I am not going to stand up to show pride in a flag for a country that oppresses black people and people of color," Kaepernick told NFL Media after Friday's game. "To me, this is bigger than football and it would be selfish on my part to look the other way. There are bodies in the street and people getting paid leave and getting away with murder."
The 49ers acknowledged in a statement that Kaepernick sat on the team's bench during the national anthem before San Francisco's game against the Green Bay Packers in Santa Clara, California.
"The national anthem is and always will be a special part of the pregame ceremony," the statement said. "It is an opportunity to honor our country and reflect on the great liberties we are afforded as its citizens. In respecting such American principles as freedom of religion and freedom of expression, we recognize the right of an individual to choose to participate, or not, in our celebration of the national anthem."
Kaepernick told NFL Media that he did not tell the team he was planning to protest the national anthem.
"This is not something that I am going to run by anybody," he said. "I am not looking for approval. I have to stand up for people that are oppressed. ... If they take football away, my endorsements from me, I know that I stood up for what is right."
Addressing reporters on a conference call on Saturday, 49ers coach Chip Kelly called Kaepernick's actions "his right as a citizen."
"We recognize his right to do that," Kelly said. "It's not my right to tell him not to do something."
Kelly added that he hadn't received any feedback from his players regarding the much-debated actions of his quarterback.
"I'm sure some of them would be aware of it after reading the accounts today, but no one has expressed anything," Kelly said. "We'll talk about it as a team tomorrow."
"Obviously, being in the military, I'm proud of that position, I'm proud of being able to defend the country, so humbled [by] other people that came before me and gave their lives so I can play on the field and run around and we can live freely in this country," Reynolds said. "But like I said, that's his right, and he's going to do what he has to do."
"I think, personally, the flag is the flag, regardless of how you feel about the things that are going on in America today and the things that are going on across the world with gun violence and things of that nature," Cruz said. "You got to respect the flag, and you got to stand up with your teammates. It's bigger than just you, in my opinion. You go up there, you're with a team, and you go and pledge your allegiance to the flag, and you sing the national anthem with your team, and then you go about your business. Whatever your beliefs are, are your beliefs.
"Colin is his own man. He decided to sit down and sit out, and that's his prerogative. But on a personal standpoint, you have to stand up there and understand that this game and what's going on around the country is bigger than just you."
"I am not going to stand up to show pride in a flag for a country that oppresses black people and people of color. To me, this is bigger than football and it would be selfish on my part to look the other way."49ers quarterback Colin Kaepernick, on his decision to sit during the national anthem
Kaepernick also did not stand for the national anthem during the other preseason games, but he wasn't dressed for those contests because of tightness in his right shoulder.
NFL spokesman Brian McCarthy said Saturday that "players are encouraged but not required to stand during the playing of the national anthem."
Pro Football Talk initially reported that Kaepernick did not stand during the anthem. He was not asked about his decision during his postgame news conference, which was held before the Pro Football Talk report.
Kaepernick, who is biracial, was adopted and raised by white parents. He has been outspoken on his Twitter account on civil rights issues and in support of the Black Lives Matter movement.
Numerous high-profile athletes have spoken out about civil rights issues in the wake of gun violence throughout the United States. In July, Dwyane Wade, LeBron James, Carmelo Anthony and Chris Paul opened the ESPYS with a call for social change and an end to violence, and WNBA players wore warm-up shirts to show solidarity after shootings in Minnesota and Baton Rouge, Louisiana.
Wade's cousin, Nykea Aldridge, was killed by gunfire in Chicago on Friday, a day after Wade participated in a series of panel discussions on gun violence hosted by The Undefeated on ESPN.
Kaepernick told NFL Media that he had thought about going public with his feelings for a while but said, "I felt that I needed to understand the situation better."
In a series of tweets on Saturday, Giants offensive lineman Justin Pugh reiterated his position on why he stands for the national anthem.
I will be STANDING during the National Anthem tonight. Thank you to ALL (Gender,Race,Religion)that put your lives on the line for that flag— Justin Pugh (@JustinPugh) August 27, 2016
@CJDeuce_ it's disrespectful to all the men and women who put their lives on the line to protect this country.— Justin Pugh (@JustinPugh) August 27, 2016
To clarify I'm not saying I know what it's like to walk in someone's shoes, I don't. Just stating what the National Anthem means to me— Justin Pugh (@JustinPugh) August 27, 2016
Kaepernick joins team sports athletes, including Mahmoud Abdul-Rauf and Carlos Delgado, in refusing to participate during patriotic American songs. Abdul-Rauf was suspended one game by the NBA in 1996 for not standing during the national anthem, saying the United States had a history of tyranny and doing so would conflict with his Islamic beliefs. He later agreed to stand and pray silently during the song. Delgado would leave the field in 2004 during "God Bless America" in protest of the Iraq War.
Kaepernick made his preseason debut on Friday against the Packers. He went 2 for 6 passing for 14 yards and added 18 yards on four carries in the 49ers' 21-10 loss.
Kelly was asked Saturday if he expects Kaepernick to make the 53-man roster.
"Yeah, he's competing with Blaine [Gabbert] to see who our starting quarterback is going to be," Kelly said. "We haven't had any discussions in terms of starters right now. Our whole focus today was really making our cuts to 75."
ESPN staff writer Nick Wagoner and The Associated Press contributed to this report.