This article was originally posted on PEOPLE.
Serena Williams is speaking out about the increasing police violence of unarmed African Americans.
In a candid and powerful Facebook post on Tuesday, the athlete expressed how she fears for the safety of her 18-year-old nephew.
Williams, 35, shared what had happened earlier in the day when she asked her nephew to drive her to her meetings.
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"In the distance I saw cop on the side of the road. I quickly checked to see if he was obliging by the speed limit. Than I remembered that horrible video of the woman in the car when a cop shot her boyfriend," she wrote, referencing the shooting of Philando Castile, whose death in Minnesota was captured on video by his girlfriend.
"All of this went through my mind in a matter of seconds. I even regretted not driving myself. I would never forgive myself if something happened to my nephew. He's so innocent. So were all 'the others,'" said Williams, whose half-sister was killed in a 2003 drive-by shooting in Compton, California.
The tennis champion's post comes just days after the deaths of two African American men Keith Lamont Scott and Terence Crutcher, both who were fatally shot by police in Charlotte and Tulsa, respectively.
"I am a total believer that not 'everyone' is bad It is just the ones that are ignorant, afraid, uneducated, and insensitive that is affecting millions and millions of lives," Williams continued in her post.
She concluded, "I had to take a look at me. What about my nephews? What if I have a son and what about my daughters? As Dr. Martin Luther King said 'There comes a time when silence is betrayal.' I Won't Be Silent."
Williams previously spoke out about police brutality and gun violence in October 2015, when she offered her support of Black Lives Matter.
Later that day, police shot and wounded an African American man in El Cajon, California. A woman close to the scene captured the shooting on video.