Colin Kaepernick wore socks depicting police officers as pigs 3 weeks ago, and people are starting to notice

Colin Kaepernick's stance on social injustice has been occurring for longer than anyone realized.

Before he sat down during the national anthem during a San Francisco 49ers preseason game this year, Kaepernick had also been posting about social injustice on Instagram for several months.

The latest discovery is a small but not-insignificant message Kaepernick made in practice on August 10, when he wore socks that depicted police officers as cartoon pigs.

It seems to have gone almost completely unnoticed until recently.

Ben Margot/AP

A closer look in this photo, where he was stretching next to fellow quarterback Blaine Gabbert:

Ben Margot/AP

Cam Inman of the Bay Area News Group tweeted a picture of Kaepernick that day, and the socks can also been seen:

Kaepernick has spoken openly about his protest and about police brutality in the US.

"There's a lot of things that need to change," Kaepernick said on Sunday (via the San Francisco Chronicle). "One specifically? Police brutality. There's people being murdered unjustly and not being held accountable. People are being given paid leave for killing people. That's not right."

Kaepernick also said that police officers needed more training.

Many have not approved of Kaepernick's statements. Martin Halloran, the San Francisco Police Officers Association president, said in a letter that Kaepernick had "embarrassed himself, the 49ers organizations and the NFL based on a false narrative and misinformation that lacks any factual basis."

Kaepernick has said he plans to continue sitting during the national anthem and is working on other projects to shed light on social injustice. The move has rankled NFL executives, many of whom reportedly believe that Kaepernick's stance could lead to the end of his football career.

Kaepernick is expected to play in the 49ers' final preseason game on Thursday night.