InterAgency Board (IAB): Integrating Law Enforcement, Fire, and Emergency Medical Services during Active Shooter / Hybrid Targeted Violence Incidents [open pdf - 444KB]
"High-threat events, although not a new phenomenon for the first responder community, continue to increase in incidence and complexity. From 'lone wolf' attacks to coordinated Hybrid Targeted Violence (HTV) incidents, these events pose significant operational challenges to public safety agencies. They are characterized by a spectrum of potential threats, including but not limited to:  One or more perpetrators, often well-trained, operationally knowledgeable, and willing to die  Well-planned operations using military tactics, often with effective communications and external coordination  Multi-capacity high-velocity ballistic and explosive fragmentation weapons  Hazardous, toxic materials requiring decontamination  Fire, to increase damage and shape and complicate the response  Intentional delayed secondary attacks on first responders  Austere and complicated operational conditions created intentionally by perpetrators and compounded by limitations on number and capabilities of response personnel."
InterAgency Board: https://iab.gov/