Kepler wore the mask amid continued protests against police brutality in the wake of the death of George Floyd, who was killed by a Minneapolis officer. A video of Floyd being pinned on the ground by a cop went viral, leading to the firing of the four police officers involved.
Shortly after posting the story, Kepler deleted it and said he "wasn't aware what the mask supported," according to Mark Townsend of Yahoo Sports.
Kepler later issued a formal apology on his Instagram story:
"Earlier, I posted a photo of me in a mask that was sent to me by a company, to wear during the pandemic," Kepler wrote. "I had no idea that the mask had any underlying inferences - I simply thought it looked good. After I was informed, I immediately took down the post.
"I take complete responsibility for not knowing what I was wearing. I am truly sorry for the hurt and pain my actions have caused, especially now. Racism has no place in our world and I do not in any way support the actions that we all witnessed that led to George Floyd's passing. My sympathies are with the Floyd family."