The wack job used good tactics, He stayed mobile, did the unexpected. Attacked from a surprise position, didn't telegraph his intent until he was in an optimum firing position. Used a near perfect weapon for in close CQB engagements. And got lucky.
The fact that he didn't kill anyone is due the fact he was an idiot. Poor ammo selection, little to no training in the type of engagement he involved himself.
The officers fought back from a severe disadvantage, and won, based on luck and training. They won by a very narrow margin. Poor ammo on there part, and little to no awareness of what was going on around them allowed the shot gunner to get in a good position to attack.
I hope they all recover, and I hope they fix the problems that got them into such a bad situation.