My guess would be that there had just been some sort of an inside joke about who would get to the phone first. White House correspondents are colleagues as well as competitors.
Did the general public have much respect for the Japanese as potential adversaries before the war? I’m guessing that until details emerged, a lot of people might have thought any attack Japan could mount on Hawaii would have been a pesky annoyance at best.
This was certainly the case by the end of the war.
If there is anything in the Geneva conventions about this, I wonder if it draws a distinction between soldiers and officers. (Since the caption in the OP’s photograph indicates the deceased was a lieutenant.)
The First Geneva Convention (1864) deals with armed forces in the field. Article 17 requires (among other things) that “parties to the conflict . . . shall further ensure that the dead are honourably interred, if possible according to the rites of the religion to which they belonged, that their graves are respected, grouped if possible according to the nationality of the deceased, properly maintained and marked so that they may always be found.”
Article 120 of the Third Geneva Convention (1929) deals with deceased prisoners of war, and is in similar terms.
It doesn’t explicitly mention military honours, only honourable interment, but since it refers to members of the armed services state parties understand that to mean military honours. There is no distinction made in the Treaty between officers and enlisted soldiers, though I suppose it is possible that the military traditions of some countries would prescribe greater honours for commissioned officers.
I’ve been looking an failing to find out exactly what “military honors” means. I haven’t found anything about rules for enemy soldiers. There’s quite a bit about honors for deceased American veterans. The military provides an honor guard of at least two soldiers, at least one of them from the same services as the deceased. There is a flag given for presentation to the next of kin, and a bugler (or recording) to play Taps. Not everyone is eligible for the gun salute – I haven’t found out why yet.
I’m guessing it was taken by the official White House photographer, who would have been warned about what was going on in the briefing room.
It’s also possible that the briefer said something like “On your marks, get set, GO!” right before the SS opened the door to let them out. Everyone would have been prepared and sanguine about the ensuing rush to file.