If he died while in the military during WWII, there should be an Individual Deceased Personnel File (IDPF) for him. To get it, make a request to the following:
U.S. Total Army Personnel Command ATTN: TAPC-PAO (FOIA) 200 Stovall Street Alexandria, VA 22332-0404
Even though this says "Army", it is the repository for IDPF's for all branches for WWII.
Give them as much info on him as you can, and be sure to state that you are asking for his IDPF through the Freedom of Information Act. You should get acknowledgment of receipt of your request within a few days. If they have the file, it could take several months before you get info.
If you want to check this before writing, their telephone number is (703) 325-4053. They can confirm address, etc, for you, but you won't be able to get any info on him over the phone.