Massacres and serial killers have, of course, been well documented throughout US history. But did the phenomenon of so-called “spree killings” - the apparently random slaying of many victims in a few minutes or hours - occur before the advent semiautomatic guns?
The worst spree/mass-murder perpetrated by Andrew Kehoe at the Bath Consolidated School in 1927 was without the use of "modern" firearms.
Without going into exhaustive detail, Kehoe treasurer was on the school board and vehemently disagreed with how the superintendent and other board members were spending the budget. For reasons not totally known, Kehoe smuggled a whole shit-ton of dynamite into the basement of the school over time (he was an electrician, and performed maintenance on the school's boiler, in addition to being the area's go-to guy for dynamite to blast stumps).
One day in May of '27, Kehoe killed his wife, rigged his house and shed to blow, and took off for the school at about 8:30 in the morning. Plenty of witnesses saw him leave his farm.
The first batch of explosives at the school had been rigged previously to blow at 8:45 AM. 38 people were killed in the initial blast. Kehoe got to the school about 30 minutes after the bomb had gone off, called the superintendent over to his truck, and eyewitnesses report the two men wrestling over a rifle before explosives in the truck detonated, killing more. Total death toll was 58, all of them within about an hour of each other, except for those who died of wounds later. I'd most definitely class that as a "spree"
Then, less-spectacular is the story of Rober Charles, a man who killed seven police offers over a period of a few days in 1898. The weapon was listed as "a rifle", which in 1900 was almost certainly a lever gun or single-shot. Will Reyonolds in 1900, he killed 6-7 peoplein the space of a day.
Then, do we count things like the Hinterkaifeck murders in 1922 Germany, where over the course of an evening an entire family was killed by somebody with a mattock?
Also, even though it's a bit of a stretch, Charles Whitman did most of his killing with a bolt-action Remington hunting rifle from the University of Texas clock tower, despite having some semi-auto weapons on his person.
Of couse, I'm leaving out all of the 1800's/early 1900's serial killers that killed for a long period of time, spaced out by months or years. People like Belle Gunness, Jack the Ripper, etc.