By circa 5 AD, Emperor Ping appeared to have grown out of a heart condition that he had suffered from, and it became plain that he resented Wang Mang for slaughtering his uncles in 3 AD and not allowing his mother to visit him in the capital, Chang'an. Wang Mang therefore resolved to murder the emperor. In the winter of 5 AD, Wang Mang gave pepper wine (considered in those days to be capable of chasing away evil spirits) to the 14-year-old emperor, but had the wine spiked with poison. As the emperor was suffering the effects of the poison, Wang Mang wrote a secret petition to the gods, in which he offered to substitute his life for Emperor Ping's, and then had the petition locked away. Historians generally believe that Wang Mang had two motives in doing this—to absolve himself of involvement in the poisoning if Emperor Ping recovered from the poisoning, and to leave evidence of his faithfulness for posterity. After a few days of suffering, Emperor Ping died making Empress Wang a widow at the age of 13. After Emperor Ping's death, Wang Mang assumed the unprecedented title of acting emperor (假皇帝).