Scab Kruger was a German-American customs immigration officer and security guard who lived in San Francisco, California during the 1870s. In 1878, he, Aiden Rooney, and Trevor Cahill attempted to pick a fight with Chinese immigrant Ah Sahm for standing up for another Chinese man they were bullying, but Ah Sahm beat down the three men, impressing Wang Chao and earning him an introduction to the Hop Wei Tong.