San Francisco's District Attorney's Office charged a sheriff's deputy on Friday for allegedly assaulting a hospital patient and then filing a fake report about it, the San Francisco Chronicle reported. 

Michael Lewelling, a patrol deputy for San Francisco's Sheriff's Department, filed a police report for a man he said attacked him with a wooden cane at San Francisco General Hospital on Nov. 3.  

Deputies later found out that wasn't so because, according to video evidence obtained by investigators, Lewelling was the one who began the assault. 

The patient was sleeping in the hospital emergency room waiting for an appointment when Lewelling began talking to him after he woke up, the attorney's office told the Chronicle.

When the man got up with his cane to walk away, Lewelling allegedly grabbed his collar and shoved him back into the chair he was sleeping in. The deputy then began choking the man, according to the video. 

After the incident the unnamed patient was arrested. But he was released the next day when prosecutors declined to press charges, the newspaper reported. Instead the district attorney's office launched an investigation into the deputy. Lewelling was arrested six weeks later. 

"The fact that a sheriff's deputy allegedly battered a patient at San Francisco General Hospital is unnerving," District Attorney George Gascon told the Chronicle. "What's worse is that he's also alleged to have perjured himself on a police report, unforgivable conduct that led to the arrest of the innocent victim."

Lewelling, who was assigned to patrol the hospital in 2013, was charged with filing a false police report, filing a false instrument, assault under the color of authority and battery. He turned himself into the authorities and was held on $138,000 bail.

"The San Francisco Sheriff's Department places paramount value in maintaining the public trust bestowed upon peace officers," the department said according to the newspaper. "To that end, the San Francisco Sheriff's Department is committed to holding its employees accountable for their conduct."