The actress Afton Williamson, a star of the ABC crime series “The Rookie,” said Sunday that she faced sexual harassment and assault, racial discrimination and bullying while working on the show’s first season and that those experiences were why she would not be returning for a second season.

In an Instagram post, which included a black-and-white illustration of the police officer she plays on the show, Ms. Williamson said that the head of the hair department had made “racially charged inappropriate comments” to her and also sexually assaulted her at a wrap party. The actress also said that a recurring guest star had sexually harassed her and that executive producers had bullied her.

Ms. Williamson, who announced at the end of July that she would not return to “The Rookie,” also criticized the show’s handling of the claims, saying they were not adequately investigated or handled appropriately.

On Monday morning, ABC’s entertainment president, Karey Burke, said at a Television Critics Association media event at the Beverly Hilton in Beverly Hills, Calif., that she did not have “a lot of answers” about how the network planned to respond.