According to Japanese researcher Haneda Toru (羽田亨) he was the same person as Uyghur general Jueluowu (掘羅勿) who rebelled against Zhangxin Qaghan.
[1] However, according to Michael Drompp, Qasar was a puppet ruler who was raised to the throne by Jueluowu.
Against usurpation, Uyghur general Külüg Bagha (Chinese: 句禄莫和; pinyin: Jùlù Mòhé) fled to Yenisei Kyrgyz and appealed for help.
Using opportunity, Külüg Bagha and 100000 Kyrgyz forces invaded Ordu-Baliq and burned the city.
[3] Following Kyrgyz sack of capital, Uyghur minister Sazhi (馺职) and Pang Tegin (庞特勒) together with fifteen clans went to the land of the Karluk (葛逻禄) for refuge.