On Monday evening, a grand jury opted not to indict Darren Wilson, a Ferguson police officer who was responsible for the fatal shooting of unarmed African American youngster Michael Brown.

The shooting itself led to violent protests and clashes on the streets of Ferguson, Missouri, and the grand jury’s decision only rekindled the anger. Even notable celebrities and athletes have come forward publicly on twitter to condemn the decision, including world No. 1 Serena Williams.

Wow. Just wow. Shameful. What will it take???

— Serena Williams (@serenawilliams) November 25, 2014

Williams concluded her 2014 season with her third consecutive WTA Finals title win in Singapore. Her win guaranteed her the year-end No. 1 ranking. The 18-time Grand Slam champion won seven titles overall this season, including the US Open title. She was awarded the WTA Player of the Year award for her accomplishments.

“It’s been a really difficult year for me. I don’t think I’ve had such an up and down year,” she said. “I started out well with Brisbane; then didn’t do well in Australia; then I did well again in Miami. It was really up and down. I ended the year well.”