Bao, an associate medical examiner for Volusia County, was fired last week, authorities said.
Authorities provided CNN with a copy of the termination letter, which said Bao was given a chance to resign.
He didn't, and was fired Friday, CNN reported.
Bao has hired a lawyer and filed a complaint against the county, court documents indicate.
Bao's attorney, Willie Gary, said he plans to file a lawsuit for discrimination, job harassment and wrongful termination.
In February 2012, Bao performed an autopsy on Trayvon Martin, after the 17-year-old was killed by George Zimmerman.
During Zimmerman's trial, Bao altered his testimony on a number of key points in the case, including how long Martin was alive after he was shot and if the marijuana in his system could have affected his behavior.
In July, a jury found Zimmerman not guilty of second-degree murder and manslaughter charges.