Im not putting sole blame on the Range OIC, the article says that the RSO was an expert on the claymore so the RSO is the one who should have made sure things were good to go. However the article also says
$1:
Watts had the authority to either move the soldiers further away or cease the exercise altogether, and was therefore ultimately responsible for what happened.
Again this isnt the failing of just the OIC, which is why more than him are up on charges.
Training should have been stopped at the higher level, or at the very least these guys should have cracked open a fucking pub.