Sigel, who had been a missionary in Chinatown, was found strangled inside a trunk on June 18, 1909, in the apartment of the prime suspect, a Chinese man named "William" Leon Ling, a waiter in a Chinese restaurant.

[1] Sigel's mother taught a Chinese Sunday school class in St. Andrew's Church at 127th Street and Fifth Avenue,[2] while Sigel did missionary work at the Chinatown Rescue Settlement and Recreation Room,[2] reaching out to "American, English, German, French, Hebrew, Italian, [and] Bohemian" girls who had gotten involved with drugs and prostitution.

[3] Four years prior to the murder, Leon had kept a chop suey restaurant on Amsterdam Avenue, close to the Sigel home, and Sigel and her mother had first met Leon there during missionary rounds of the local Chinese restaurants.

[1] It was speculated that the motive for murder might have been jealousy, as Chu Gain, manager of the Port Arthur Restaurant on Mott Street, was also found to be in possession of recent love letters from Sigel.

Chu reported that he had recently received an anonymous letter threatening Sigel's life if they did not cut off their relationship.