Estrada Cabrera often employed brutal methods to assert his authority. Right at the beginning of his first presidential period he started prosecuting his political rivals and soon established a well-organized web of spies. One American ambassador returned to the United States after he learned the dictator had given orders to poison him. Former president Manuel Barillas was stabbed to death in Mexico City. Estrada Cabrera responded violently to workers' strikes against UFCO. In one incident, when UFCO went directly to Estrada Cabrera to resolve a strike (after the armed forces refused to respond), the president ordered an armed unit to enter a workers' compound. The forces "arrived in the night, firing indiscriminately into the workers' sleeping quarters, wounding and killing an unspecified number."