My brother was a career army officer. My father was career air force.
Friendly fire happens. Nobody likes to talk about it, and certainly not to the families of the soldiers killed this way, but it is a reality of war. What he sees as a 'coverup' is probably pat's fellow soldiers trying to leave the family and the country with a happier, though dishonest, story of his death.
Of course they shouldn't have done it, but I am not willing to crucify them for doing it.