Diagnosed with bone cancer, likely resulting from his exposure to radiation during his work on the Manhattan Project. The exact type of cancer is not definitively known but is suspected to be related to radiation exposure.

Experiences a rapid decline in health as the cancer progresses. He suffers from severe pain and is confined to a wheelchair. Despite his deteriorating condition, he continues to work and consult as much as possible.

Dies at the age of 53 at Walter Reed Army Medical Center in Washington, D.C. His death is a significant loss to the scientific community and the US government. He was buried with full military honors at Princeton Cemetery.