random strangers. Their motives vary. One motivation for mass murder is revenge, but other motivations are possible, including the need for attention or fame. Acting on the orders of Joseph Stalin, Vasili Blokhin's war crime killing of 7,000 Polish prisoners of war, shot over 28 days, was one of the most organized and protracted mass murders by a single individual on record. Law enforcement response and countermeasures Analysis of the Columbine High School massacre and other incidents where law enforcement officers waited for backup has resulted in changed recommendations regarding what victims, bystanders, and law enforcement officers should do. In the Columbine shooting, the perpetrators, Eric Harris and Dylan Klebold, were able to murder 13 people, then commit suicide before the first SWAT team even entered the school. Average response time by law enforcement to a mass shooting is typically much longer than the time the shooter is engaged in killing. While immediate action may be extremely dangerous, it could save lives which would be lost if victims and bystanders involved in the situation remain passive, or law enforcement response is delayed until overwhelming force can be deployed. It is recommended that victims and bystanders involved in the incident take active steps to flee, hide, or fight the shooter and that law enforcement officers present or first arriving at the scene attempt immediately to engage the shooter. In many instances, immediate action by victims, bystanders, or law enforcement officers has saved lives. However, law enforcement programs and actions have so far been unable to reduce the total number of incidents. In 2020, a record number of 600 mass shootings occurred. Criticism as an analytical category Commentators have pointed out that there are a wide variety of ways that homicides with more than several victims might be classified. Such incidents can be, and have been even in recent decades, classified many different ways including "as a mass shooting; as a school shooting; as mass murder; as workplace violence...; as a crime involving an assault rifle; as a case of a mentally ill person committing acts of violence; and so on." How such rarely occurring incidents of homicide are classified tends to change significantly with time. "In the 1960s and 1970s,... it was understood that the key feature of [a number of such] cases was a high body count. These early discussions of mass murder lumped together [a variety of] cases that