I'll give you that point, SirSloop, but I was referring less to non-chalance, and more to poor tactics and readiness.
That said, a friend of mine was a corrections officer in the Florida panhandle. He wasn't remotely non-chalant, yet he froze like the proverbial deer in the headlights when an inmate came at him with a shiv. Took a downward stab in the shoulder as a result. Other CO's restrained the guy.
Met that CO in the dojo, a few months after the incident. He never wanted to freeze up like that again.
Next time he got attacked, it was by a trustee on a road crew, who was wielding a bush axe. My friend took the axe and knocked out the trustee with one entering disarm. Training made a big difference, there.
Had another acquaintance, a Marine, who was moon-lighting as a reserve cop in Riverside, CA. Went to assist a team that was taking down a gang's house. My acquaintance was ready to deal with big, bad gang-bangers, but wasn't prepared to shoot a 13 year old; the kid pulled a cheap .22 or .25, and shot the Gunny in the gut. Luckily, the vest worked. After that, the Gunny was much more mentally prepared to shoot a kid, if necessary.
Sometimes, people just don't know how to react. Training can make a world of difference. Where training fails, experience will take over, assuming one survives the experience.