A national controversy that began on the West Coast and extended to the Pacific Northwest grew Sunday when four members of the Miami Dolphins kneeled during the national anthem as the National Football League attempted to mark the 15th anniversary of Sept. 11 in solemn fashion.

>> Miami coach Adam Gase addresses national anthem protest

Running back Arian Foster, safety Michael Thomas, linebacker Jelani Jenkins and receiver Kenny Stills kneeled on the Dolphins’ sideline in protest of racial inequality. The host Seattle Seahawks, including coach Pete Carroll, ended days of speculation about plans for a team-wide demonstration of unity by interlocking arms while uniformed Air Force veteran and firefighter Keith Taylor sang “The Star-Spangled Banner.”

Moments earlier, the four kneeling Dolphins stood at attention during a moment of silence in honor of the victims of Sept. 11.

The Dolphins, who lost the season opener to the Seahawks, 12-10, took a cue from San Francisco 49ers quarterback Colin Kaepernick, who sat for one rendition of the anthem and kneeled for another to show his objection for the way African-Americans are treated in the United States and the controversial handling of police violence.

Kaepernick’s actions triggered an emotional debate, with some saying it was the only way his concerns could be heard in a transcendent manner. Others argue it’s disrespectful of the flag and the military on any day — and doubly so on Sept. 11.

It struck such an emotional chord that many fans posting comments on social media said they would stop supporting the Dolphins if they failed to stand at attention during Sunday’s anthem.

Coach Adam Gase said he was unaware what his players planned, only that they assured him, “We’re not looking to do anything disrespectful.”

>> Read more trending stories

Gase added, “There’s nothing I’m able to say one way or the other because every person, it’s their opinion, it’s their right and my job is to coach a football team.”

Shortly after the anthem, the Dolphins issued a statement:

“We encourage all members of our organization to stand at attention during the national anthem out of respect and appreciation for the freedoms we are afforded as Americans. We also recognize that it’s an individual’s right to reflect during the anthem in different ways. We respect these liberties and appreciate the sacrifices that everyone has made for our country, especially on this day of remembrance. We hope today’s events will continue a respectful and thoughtful dialogue in our community on unity, inclusiveness and togetherness.”

CBS, which televised the game, downplayed the Dolphins’ protest as it unfolded. Although cameras found Foster during the anthem, he was obscured, so it was unclear to viewers if he was standing. A tight shot of Thomas gave the impression he was standing.

CBS soon had sideline reporter Evan Washburn report on the Seahawks’ demonstration, but it wasn’t until later that play-by-play man Ian Eagle informed viewers that the CBS crew “counted four Dolphins from our sight line” who kneeled. Eagle then named them.

“These guys are my teammates and everyone has a reason for doing what they’re doing,” quarterback Ryan Tannehill said after the game. “That’s America. You just have to stand up for what you believe in and when the national anthem is over, be ready to play.”

>> Seahawks stand together, link arms during national anthem before season opener

With the Seahawks making vague comments about a team demonstration, fans braced for the opening of the season Sunday. Would Sept. 11 be awash with rebellious acts and possibly boos? In the end, a solemn tone prevailed in most stadiums. First responders, members of the military and players unfurled flags that covered most of the fields.

“It’s Sunday and here in America that means it’s time for football,” President Obama said in a video message played before all the games. “But on this day 15 years ago, the world was shaken, towers crumbled and thousands of Americans lost their lives.”

In Philadelphia, Vice President Joe Biden stood next to Eagles coach and former Dolphins quarterback Doug Pederson, holding the flag as a trumpeter played the anthem.

But in Kansas City, Chiefs cornerback Marcus Peters held a black-gloved fist aloft during the anthem, copying the protest by U.S. track athletes John Carlos and Tommie Smith on the medal stand at the 1968 Mexico City Olympics.

In Nashville, Titans linebacker Avery Williamson wore special cleats paying tribute to Sept. 11 while risking a fine from the league. Teammates and even police unions rallied to his defense, saying they would pay any fine.

>> Titans player who wished to honor 9/11 victims with special cleats gets major pushback from the NFL

Palm Beach Post staff writer Dave George in Seattle contributed to this story.