This has happened occasionally and will happen again. What would your better way to do it be? It’s too easy to become sloppy and complacent when you aren’t in a live fire situation, keeping your awareness of what and whom is around you, where your friends are and where the enemy is.
This does not happen this way too often. There was a live fire incident at Camp Pendleton in 1970 on a range where we were training. I knew the kid killed and before I left training saw the incident report. Ruled out somebody with a grudge or human error. All indications were one in a million event of an explosion which threw rocks into the air and deflected a large fragment of a round passing over the explosion downward and into the guy who was prone, taking cover. It happens and part of the training risk. Knew of one guy who was about to rappel and had a brain fart when it came time to secure his line.
A week later all live fire was banned, due to fire danger. I always thought the "split bullet" theory was a little odd. I was learning, even then, that maybe "The Word" was rumor and gossip writ large.