OAKLAND, Calif. (KRON) — Former Oakland Police Chief LeRonne Armstrong has officially appealed his firing, a spokesperson announced Thursday. Armstrong was fired by new Mayor Sheng Thao Feb. 15.

Armstrong’s attorney sent a letter to the city on Wednesday, officially beginning the appeal process. As part of that process, an official will review the evidence and make a recommendation to the city about whether to uphold his firing.

“This action is the first step towards litigation by Chief Armstrong and his attorneys against the City of Oakland for his retaliatory and wrong termination by Mayor Sheng Thao.  It should come as no surprise to the public that when Chief Armstrong came within inches of removing federal oversight that Federal Monitor Robert Warshaw concocted false and misleading allegations to keep his lucrative contract in place,” said Sam Singer, a spokesperson for Armstrong.

Thao said she lost confidence in Armstrong after an Oakland sergeant allegedly was involved in a hit-and-run crash. Armstrong failed to properly discipline the sergeant and later downplayed the gravity of the misconduct, she said.

“Chief Armstrong made a number of statements that troubled me. Chief Armstrong said these were not incidents where officers behaved poorly. He stated that he did not believe these incidents reflected systemic problems,” Thao said.

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Armstrong was first placed on administrative leave in January after an investigation by Federal Monitor Robert Warshaw found that he did not handle misconduct allegedly committed by the sergeant.

Thao’s decision to fire Armstrong has been met with backlash from several community groups in Oakland. On Monday, the NAACP held a rally in support of Armstrong.