A nursing assistant was arrested Thursday by the California Department of Justice for allegedly sexually abusing an elderly patient at a Concord rehabilitation facility. Arian Mojaddidi is facing one felony charge of performing a lewd act by a caretaker upon a dependent adult, state prosecutors announced Friday. Mojaddidi allegedly abused an 86-year-old patient in April at Concord Post Acute, a skilled nursing facility specializing in short-term, long-term and hospice care, according to a news release from the state DOJ. The patient suffers from “diminished capacity,” but prosecutors didn’t say why they were in the facility or how state officials learned of the alleged abuse. Officials with Concord Post Acute didn’t immediately respond to a request for comment Friday afternoon.