A family friend's son died of leukemia

He was supposed to graduate this school year under the degree of Bachelor of Science in Civil Engineering. But he died last month. He just complained of stomachache. The day he was brought to the hospital, the doctor told his parents he has to undergo operation. But when they checked his blood, they found out he has leukemia. When his parents asked for the cancer stage, the doctor replied there is no stage for his case. The cancer cells are spreading four times faster. He died after 9 days which makes it all the more painful to his family. Why so fast? How come they saw no signs when it was spreading in his body so quickly? What kind of cancer is this?