The San Francisco sheriff’s deputy who allegedly assaulted a hospital patient last month and then claimed he was attacked by the patient is scheduled to make his first court appearance Friday. Deputy Michael Lewelling, 33, was charged Friday with four felonies, including assault and perjury, and one count of misdemeanor battery in connection with the Nov. 3 incident at San Francisco General Hospital, the District Attorney’s Office announced. Sheriff Ross Mirkarimi on Sunday called the alleged assault “unacceptable” and said his department will launch an internal personnel investigation into Lewelling, who was placed on unpaid administrative leave. “Like law enforcement everywhere, deputy sheriffs are entrusted with great responsibility and authority to serve public trust,” Mirkarimi said. “When that trust is broken, we act immediately to address the breach.” The charges came about through the newly-formed criminal investigation unit of the Sheriff’s Department, Mirkarimi said. The unit conducted a six-week investigation into the case and eventually uncovered video surveillance that reportedly showed Lewelling assaulting the victim. Lewelling, according to the charges, was assigned to the patrol unit of the hospital the morning of Nov. 3 when he approached the patient, who was hunched over in a chair sleeping in the emergency room’s waiting area. Prosecutors said they appeared to speak to each other, and the patient slowly stood up, using a cane for assistance. The patient then took a step toward the exit when Lewelling allegedly grabbed the back of his collar, pulling him back into the seat and knocking the cane away. A few seconds later, Lewelling appears to grab the patient’s throat and choke him before placing him under arrest, prosecutors said. Prosecutors added that the victim never appeared to raise his cane in a threatening manner. After the incident, Lewelling filed a police report claiming that the victim had attempted to assault Lewelling with a wooden cane. The victim was arrested, but the District Attorney’s Office declined to file charges and released the victim. “There were contradictions about the incidents and the arrest resulting from the incident that caught the attention of our [criminal investigation unit], and my attention,” Mirkarimi said of why his department then began looking into the case, though he declined to be more specific. The video surveillance of the incident was presented to the District Attorney’s Office on Friday, the same day Lewelling was arrested. He posted $138,000 bail about 8 p.m. that day and is due in court for his arraignment at 1 p.m. Dec. 26. Mirkarimi said he is unaware of any prior disciplinary issues involving Lewelling.