Shotgun breaching is definitely a technique, but I've never done it on metal doors with metal door jams ((one statement somewhere in the news stated there was a metal door jam; I'm assuming that meant the door frame was metal, & not that there was some metal bar or locking device on the door)). ((Caveat: we breached metal laminate doors that were foam filled, so I'm not saying there isn't a technique for ballistic breaching of metal doors, just that I don't recall ever doing it with a door hung on a metal door frame, like found in commercial settings. We used explosive breaching for all kinds of doors, & all I remember doing with metal door frames was explosive breaching)).
From what we were taught on ballistic breaching, rifles & pistols were absolutely a no-go due to the injury hazard of high velocity solid projectiles over penetrating into the room (non-combatants/hostages in room) or ricochet hazard to assaulters in hallway/outside of room. Now, if there was a clear PID of the shooter thru a door window, I would have placed several rounds of 5.56 thru the window or door in hopes rounds would penetrate & at least wound the nutjob.
Regarding the training conducted in March, I'm wondering if the training included live-fire, or just dry-fire or force-on-force. And if live fire training, did it include mechanical, ballistic, or explosive breaching techniques. I am willing to bet the BORTAC guys are proficient at breaching, but a small town PD, even with a small town SWAT TM, wouldn't likely have proficiency with breaching.