What would that have done? This guy is in the US Airforce, not the IDF. This isnt like Veitnam or Korea, or any of the other genocidal actions take by the US Military, because the US military isnt the one perpetuating this genocide, Israel is. Killing some low level Air Force officer in DC isnt going to do anything to help Palestinians.
Think about it: if he had killed another member of the Air Force "for Palestine" that would be incredible propaganda for Israel. It would have done nothing but create further fuel for American support for Israel.