I can't get my head around this. Back in my day we went in. If someone said, "There's a guy with a gun in there," we went in.
In my earliest days in law enforcement there were no SWAT teams. If we didn't do it, it didn't get done. I think modern law enforcement has been brought up with the philosophy that anything more serious than a parking complaint requires a SWAT response. And I can tell you that any copper in my day who said, "I can't go in there...I might get shot," would have had a short career.
When the deal in Florida happened where the school resource officer sat outside with his thumb stuck in his fat ass listening to kids die I thought it was a one-off, an aberration.