[Robert Teesdale]

I am hearing that the rules of engagement were “active shooter”. Does anyone know what agency is responsible for setting that? Who owns this stinking mess?

[USNBandit]

Active Shooter doesn't change the "rules of engagement." It changes the tactic. The ROE for law enforcement in this country are the same for use of force. It is based upon a concept that any use of force is the most serious type of 4th amendment seizure possible, seizing your well being and possibly your life. The two main SCOTUS cases are Garner v. Tennessee and Graham v. Connor. There can't be an ROE established that changes those legal standards.

As far as the tactic goes, active shooter implies an urgency to get into the scene and engage a person(s) shooting innocents.

[a fool in paradise]

I am hearing that the rules of engagement were “active shooter”. Does anyone know what agency is responsible for setting that? Who owns this stinking mess?

The guards at Kent State opened fire in response to what they believed (and may have been) enemy fire from the "peace" protesters.