SAN JOSE, Calif.—A gunman who killed nine co-workers at a Northern California rail yard shot himself twice in the head as sheriff’s deputies raced into a building, according to authorities who on Tuesday released body camera footage of the tense encounter. The nearly four-and-a-half minutes of footage is from one deputy who arrived minutes after the first shooting reports and while shots were still being fired at the Santa Clara Valley Transportation Authority bus and rail yard in San Jose, where 57-year-old Samuel Cassidy opened fire before killing himself. A “contact team” of deputies and San Jose police officers was immediately formed to find the gunman, who was reported to be inside a building and armed with a handgun. The body camera footage shows the team cautiously climbing stairs to the third floor, where a VTA supervisor comes out with arms raised and hands over his keycard so officers can …