"First, I send prayers to the family and friends of George Floyd, Breonna Taylor, and Ahmad Aubrey," Mahomes wrote. "As I have watched everything that has happened over the last week and even before then, I have tried to put my feelings into words.
"As a kid who was born with a black dad and white mom, I have been blessed to be accepted for who I am my entire life, but that isn't the case for everyone. The senseless murders that we have witnessed are wrong and cannot continue in our country.
"All I can think about is how I grew up in a locker room where everyone is accepted. We all need to treat each other like brothers and sisters, and become something better. Let's be the world where my little sister, generations to come, and even my future kids will grow up never having to experience these tragedies and instead love each other unconditionally! Love and unite!"
He concluded his message with the hashtag #JusticeForGeorgeFloyd.
Floyd's killing last week has sparked protests in several U.S. cities and prompted some of the world's biggest sports icons to speak out and call for social change.
NFL commissioner Roger Goodell issued a statement last week saying, "There remains an urgent need for action."