Father Cameron Faller, right, and Julio Escobar, of Restorative Justice Ministry, conduct a vigil for Kathryn Steinle, Monday, July 6, 2015, on Pier 14 in San Francisco. Steinle was gunned down while out for an evening stroll at Pier 14 with her father and a family friend on Wednesday, July 1. (AP Photo/Beck Diefenbach)SAN FRANCISCO (AP) — The gun used in the seemingly random slaying of a woman on a San Francisco pier belonged to a federal agent, a law enforcement official briefed on the matter said Tuesday.