SAN FRANCISCO—Jack Palladino, the private investigator who worked on high-profile cases ranging from the Jonestown mass suicides to celebrity and political scandals, has been placed on life support after suffering a head injury during an attempted robbery. Palladino, 70, had just stepped outside his San Francisco home on Thursday to try out his new camera when a car pulled up and a man jumped out to grab it from him, police and the detective’s stepson Nick Chapman told the San Francisco Chronicle. As the suspect grabbed the camera, Palladino fell and hit his head on the pavement, causing a traumatic head injury. Chapman said Palladino was not expected to survive after undergoing surgery to stop the massive bleeding. Police said one suspect has been arrested, with authorities on the hunt for at least one other assailant, a source told the Chronicle. Palladino was wrapping up one final case before joining his …