LOS ANGELES — The Los Angeles Police Department will reopen its investigation into the 2007 episode that led to the firing of Christopher J. Dorner, the former police officer who is wanted in three killings, department officials said Saturday night.

Mr. Dorner pledged revenge against Los Angeles police officers in a manifesto he posted online, in which he also claimed that racism in the department had led to his dismissal. He is wanted in connection with the killing of a former police captain’s daughter and her fiancé last Sunday and the shooting death of a Riverside, Calif., police officer on Thursday morning.

“I am aware of the ghosts of the L.A.P.D.’s past, and one of my biggest concerns is that they will be resurrected by Dorner’s allegations of racism within the department,” Chief Charlie Beck said in a written statement.

“Therefore, I feel we need to also publicly address Dorner’s allegations regarding his termination,” he said. “I do this not to appease a murderer. I do it to reassure the public that their Police Department is transparent and fair in all the things we do.”