Serena Williams is joining Colin Kaepernick and other athletes who are using their platform to speak out against social injustice. In a recent Facebook post, Williams mentioned she was moved to speak out after taking a drive with her 18-year-old nephew.

Williams nephew was driving her to a meeting when they past a police office. She stated that she “quickly checked to see if he was obliging by the speed limit.” Williams wanted to avoid interaction with the cop.

The tennis champ also spoke of Philando Castile’s murder in Minnesota. “That horrible video of the woman in the car when a cop shot her boyfriend,” stated Williams in her post. Her concern about all that is happening ended with a quote by Martin Luther King Jr. “there comes a time when silence is betrayal” and lastly she states “I Won’t Be Silent.”