How did people commit mass murder before the advent of automatic weapons?
Often with fire. Revolutionary War veteran Barnett Davenport is widely considered the first mass murderer in U.S. history. ... [M]ost criminologists define mass murder as the killing of at least three people in a single incident. After beating the Mallorys to death, however, Davenport burned the house down, killing their three grandchildren. ...
Guns aren’t even the most lethal mass murder weapon. According to data compiled by Grant Duwe of the Minnesota Department of Corrections, guns killed an average of 4.92 victims per mass murder in the United States during the 20th century, just edging out knives, blunt objects, and bare hands, which killed 4.52 people per incident. Fire killed 6.82 people per mass murder, while explosives far outpaced the other options at 20.82. Of the 25 deadliest mass murders in the 20th century, only 52 percent involved guns.
The U.S. mass murder rate does not seem to rise or fall with the availability of automatic weapons. It reached its highest level in 1929, when fully automatic firearms were expensive and mostly limited to soldiers and organized criminals. The rate dipped in the mid-1930s, staying relatively low before surging again in the 1970s through 1990s. Some criminologists attribute the late-century spike to the potential for instant notoriety: Beginning with Charles Whitman’s 1966 shooting spree from atop a University of Texas tower, mass murderers became household names. Others point out that the mass murder rate fairly closely tracks the overall homicide rate. In the 2000s, for example, both the mass murder and the homicide rates dropped to their lowest levels since the 1960s.
--Brian Palmer, Slate, on technological substitutes