Former NFL player Colin Kaepernick had an odd way of celebrating Thanksgiving, attending an event that appeared to serve as a rebuke to the holiday and the United States.

On Thursday, Kaepernick spoke at the "Indigenous People's Sunrise Ceremony," also known as "Unthanksgiving," on Alcatraz Island in San Francisco, California. The event is intended to celebrate the 50th anniversary of Native Americans occupying the famous island, which previously served as the site of a federal prison.

"Spent the morning at the Indigenous People’s Sunrise Ceremony on the 50 year anniversary of the Occupation of Alcatraz," Kaepernick tweeted on Thanksgiving day.

"The US government has stolen over 1.5 billion acres of land from Indigenous people. Thank you to my Indigenous family, I’m with you today and always."

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Kaepernick is no stranger to controversy and has been out of the NFL since the 2016 season. He started a national firestorm when he decided to kneel during the national anthem before games to raise awareness about perceived social injustices across the U.S. He accused NFL owners in a grievance of blackballing him from the league because of the anthem protest, but the two sides settled earlier this year.

He tweeted a video of a man proclaiming that Native Americans were taking the land by "right of discovery." The video also appeared to show him speaking to celebrants on the island.

"It's been 50 years since the occupation," Kaepernick said. "And that struggle has continued for that 50 years ... It's our responsibility to honor our ancestors and honor our elders by carrying on that struggle. Don't let their sacrifices be in vain. That's why it's important for all of us to be here today -- to show that we're together, that we're unified, that we have that solidarity. And I hope to spend many more of these with you."

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Kaepernick also apparently attended the event in 2017.

Kaepernick also retweeted an article by Washington Post writer Christopher Petrella who indicated Thanksgiving was racist.

"Antebellum campaigns to establish Thanksgiving as nat’l holiday grew up alongside colonizationist efforts to remove free Black people from U.S. Nationalization advocates mobilized white fears of Black equality to build support for holiday," he said in the post retweeted by Kaepernick.

Kaepernick released a hype video Monday, days after he worked out for a handful of NFL teams at an Atlanta-area high school in hopes of making a still-elusive return to the league.

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The video showed Kaepernick launching passes to receivers during his workout at Charles Drew High School. It also included a message to the media after his workout that he was ready to come back and compete again in the NFL.

There have been conflicting reports on whether any NFL teams are interested in the quarterback after his midseason workout. ESPN reported Sunday that no teams have reached out to Kaepernick to work him out further, while his attorney appeared on Adam Carolla’s podcast last week and said at least two teams were interested. The attorney didn’t specify which teams.

Fox News' Ryan Gaydos contributed to this report.