WASHINGTON—Jo Ann Hinckley, a constant companion to her son John Hinckley Jr. as the would-be assassin of President Ronald Reagan was gradually allowed to live outside a psychiatric hospital in Washington, has died. Jo Ann Hinckley, 95, had been her son’s primary companion as he transitioned in recent years from living at a Washington psychiatric hospital to being allowed to live with her full-time in a gated community in Williamsburg, Virginia. Barry Levine, John Hinckley’s longtime attorney, confirmed Jo Ann Hinckley’s death to The Associated Press on Tuesday. Levine said Jo Ann Hinckley died in her sleep last week. He did not provide a cause of death. Levine said Jo Ann Hinckley devoted her life to looking after her son following Reagan’s shooting. She and her husband, John “Jack” Hinckley Sr., had moved to Williamsburg to be closer to their son after a jury found him not guilty by reason …