The Santa Clara Police Union sent a letter to the 49ers saying officers may stop working team events due to Colin Kaepernick's recent behavior.

Santa Clara police chief Michael J. Sellers urged the local police union to back down from a boycott threat made this week in response to 49ers quarterback Colin Kaepernick’s protest of the national anthem, USA Today reports.

Kaepernick has been outspoken about his frustration over the way minorities, particularly African-Americans, are treated by police in the U.S. The Santa Clara Police Union sent a letter to the San Francisco 49ers this week stating the officers may stop working team events unless changes are made regarding Colin Kaepernick's recent protest and behavior. Around 70 officers regularly staff 49ers games, and Sellers said there would be no security concerns.

“I will urge the (Santa Clara Police Officers' Association) leadership to put the safety of our citizens first,” Sellers said in a statement sent to USA Today. “I will work with both sides to find a solution. In the meantime, I will ensure we continue to provide a safe environment at Levi’s Stadium.”

“Many of us in the law enforcement community have been saddened and angered by Kaepernick's words and actions,” Sellers added. “His blanket statements disparaging the law enforcement profession are hurtful and do not help bring the country together. As distasteful as his actions are, these actions are protected by the Constitution. Police officers are here to protect the rights of every person, even if we disagree with their position.”

Last week, Kaepernick chose not to stand for the anthem before San Francisco’s preseason game against the Green Bay Packers in protest of racial oppression. At Thursday’s game, he kneeled during the anthem along with teammate Eric Reid. Seahawks cornerback Jeremy Lane also sat during the national anthem ahead of Seattle’s game against Oakland.

“The board of directors of the Santa Clara Police Officer's Association has a duty to protect its members and work to make all of their working environments free of harassing behavior," the original letter from police to the 49ers obtained by NBC stated on Friday, after photos taken in early August circulated showing Kaepernick wearing socks that depicted pigs in police uniforms.

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After Thursday’s game, Kaepernick announced he will donate $1 million of his salary this season to organizations that work with and help communities.