He won victories over Zhang Zuo's forces and approached the capital Guzang (姑臧, in modern Wuwei, Gansu).
Upon Zhang Guan's subsequent arrival at Guzang, he became the regent, and he instead had Zhang Xuanjing claim the title of Prince of Liang, a title that the Jin dynasty did not confer, but continued to claim to be a Jin vassal.
He had himself made the governor of Liang Province (涼州, modern central and western Gansu) and the Duke of Zhangyi.
Once Zhang Guan became regent he became dictatorial and suspicious, making awards and punishments based on his own personal whim.
Once Song Hun heard this news, he gathered his troops and declared Zhang Guan to be treasonous, claiming to have authorization from Zhang Xuanjing's grandmother Princess Dowager Ma to kill him.