Security staffer Nation Wood -- who previously worked for former President Joe Biden and posed for a picture with Kamala Harris -- has been arrested on involuntary manslaughter charges in San Francisco ... this according to SFPD. The 25-year-old has been booked for allegedly shooting and killing a woman -- identified by the city's Office of the Chief Medical Examiner as Samantha Emge , the San Francisco Chronicle reports. Cops say they found Samantha suffering from a gunshot wound in a 22nd