Mullah Rabbani was the second most important member of the Taliban movement until he died on April 16, 2001; it was reported that he died as a result of cancer. Many analysts believe that it was Mullah Rabbani that ordered the execution of Dr. Najibullah when the Taliban took Kabul in late 1996. There were also rumors that Mullah Rabbani, and the head of the Taliban movement (Mullah Omar) had serious political differences.