The report says that he is held in custody on second-degree murder charges. The reporter notes that the military has the death penalty. But the death penalty would only be for a conviction under UCMJ art. 118. Hawaii does not have the death penalty.
The spouse was pregnant, so the possibility exists of a second charge under UCMJ art. 119a at court-martial. Death is not an authorized punishment under this article.
It does not appear the spouse is a service member.
The report notes (as we know) that civilian and military authorities frequently discuss jurisdiction when a service member is a suspect.