You have every right to be proud of your son's accomplishment. That is a fine buck for anyone, especially a young hunter. Congratulations to the hunter and to the mentor who invested in him.
My son is 7 and he was using his Remington 700 Compact in 243 with a 95gr Winchester Deer Season XP. I like to use hand loads but we have these on hand and they do a great job on deer.
The story... We got to the blind at 3:20 on Friday afternoon. I had my son and my 5 year old daughter with me. At about 3:40 a little doe came into the food plot and fed. After about 10 minutes she ran off. At 3:55 my son said, "Dad there is a buck coming and it is a buck I want to shoot." I told him to get ready and I grabbed my grunt call. I grunted to stop him and when I grunted the buck turned quartering to just a bit. Braden shot and the buck humped up and ran off. He was super excited but I was a bit concerned with the deer's reaction. After 30 minutes we went to the edge of the food plot where the deer ran into the woods to look for blood. We found none and then saw the buck get up out of his bed and run off. My boy was crushed. The most upset I have ever seen him. We immediately went back to the truck, headed home and tried to sleep. The next morning we went to area in which the buck ran and found him relatively quickly. His tears of heartbreak and disappointment the night before turned into screams of joy. As I had suspected the last second turn of the buck put Braden's bullet in the liver. But Braden learned a valuable lesson of backing out and giving the deer the night when you do not have good sign of a hit.