He immediately underwent treatment in the form of chemotherapy at the hospital and then returned to work in December, a month earlier than expected. In early 2007, Thomas said he was feeling better than he had in a long time, but he returned to the hospital for a second round of chemotherapy a month later. On June 4, 2007, Thomas was reported in serious condition, struggling with an infection while undergoing a second round of chemotherapy at Bethesda Naval Medical Center in Bethesda, Maryland. Thomas was pronounced dead that same day from complications of leukemia at 9:53 PM EST.