From 2006 to 2017, there have been more than 350 mass killings in the United States.
Well-known images from Newtown, Aurora and Virginia Tech capture the nation's attention, but similar bloody scenes happen with alarming frequency and much less scrutiny.
USA TODAY examined FBI data -- which defines a mass killing as four or more victims -- as well as local police records and media reports to understand mass killings in America. They happen far more often than the government reports, and the circumstances of those killings -- the people who commit them, the weapons they use and the forces that motivate them -- are far more predictable than many might think.
Yet no one is keeping track.
While only about 1% of all murders nationally, mass killings still happen frequently. The FBI data do not include some large states such as Florida, for example. Poor reporting by police agencies to the FBI also means some mass killings were left out, while others that don't meet the standard were included.
Erroneous and excluded cases from 2006 to 2014 leave FBI data with a
Breakups, estrangements and family arguments make up the majority of cases, though unrelated victims may be caught in the crossfire.
A breakup is the trigger behind 1 in 4 mass killings that do not involve strangers, gangs or a robbery gone wrong. Yet the examples below illustrate how holiday stress, a job loss or financial ruin can lead to extreme violence. And often, that violence occurs in families that otherwise seemed normal.
1 in 4victims were close family members -- children, siblings, spouses, etc.
76% of mass killings involve a gun. But killers also have used everything from their hands to saws to baseball bats.
Nearly 30% of victims were under age 18.
A killer wielding a multiple-magazine assault rifle is the exception. More typically, the closest available weapon is used. These are the guns killers carried with them, regardless of whether it was used. Stashes in cars, at home, etc. are not included.
Many mass killers do not face prosecution. About a quarter commit suicide after the crime, and others are killed by police. Still more are deemed incompetent due to mental illness. When cases do go to trial, they can often take years because of the death penalty or other complications.
While both men and women commit mass killings, their choices of weapons and the outcomes of their cases are different.
While guns are the most common weapons, a car, a fire or nearly anything at hand can become a weapon.
As the cases below show, the killing can be planned or impulsive.
Ineffective protective orders, gaps in the mental health system, immigration bureaucracy and other lapses have been implicated in many cases.
Mass killings -- four or more killed in one incident -- happen across the U.S.
Source: USA TODAY reporting and analysis by Paul Overberg, Meghan Hoyer, Mark Hannan, Jodi Upton, Barbie Hansen and Erin Durkin; copy editing by Jim Cheng
Interactive: Juan Thomassie, Destin Frasier, Tyler Fisher, Anthony DeBarros, Andrea Fuller, Jerry Mosemak, Kristin DeRamus, Shayli Jimenez, Kristen Papa and Esley Svanas
© 2013 USA TODAY, a division of Gannett Satellite Information Network, Inc.
About this photo: Carlee Soto uses a phone to get information about her sister, Victoria Soto, a teacher at the Sandy Hook Elementary School in Newtown, Conn., on Dec. 14, 2012, after a gunman killed 26 people including 20 children. Victoria Soto, 27, was among those killed. (Photo: AP/Jessica Hill)
About this photo: Flowers and graffiti cover the steps of a home where Aaron Kyle Huff spray-painted the word "Now" before opening fire on a house full of partygoers in Seattle and killing six before taking his own life on March 25, 2006. Police are unsure why Huff wrote the word before the shootings. (AP/Ted S. Warren)
About this photo: Six caskets line the front of St. Mary's Church in Iowa City during a funeral mass for Steven Sueppel, 42, his wife, Sheryl, 42, and their four children, Eleanor, 3, Seth, 8, Ethan, 10, and Mira, 5, on March 29, 2008. Steven Sueppel killed his family late Sunday night or Monday morning, then crashed the family minivan into a concrete sign base on Interstate 80 near Iowa City, killing himself in what police are calling a murder-suicide. At the time of the murders he was out on bond, charged with embezzling $560,000 from the bank where he was vice president. (AP/ Brian Ray)
About this photo: As many as 20 bullet holes riddle the entryway of the New Life church in Colorado Springs on Dec. 10, 2007. Matthew Murray, 24, was dropped from the missionary program of New Life Church in Arvada, Colo., in 2002. Five years later, he returned to one the church's program buildings and killed two people, then drove 80 miles to the evangelical church itself, where he killed two others before committing suicide. (AP/ Kevin Moloney)
About this photo: Karen Eides, left, Tim Torres and David Gordon embrace as they kneel in front of a makeshift memorial outside Cafe Racer on May 31, 2012, in Seattle. The gunman, identified as Ian Lee Stawicki, 40, allegedly shot and killed four at the cafe, where he had been banned. A fifth person was killed when he stole her car. He killed himself as police approached. (Getty Images/ Stephen Brashear)
To analyze mass killings, USA TODAY used the FBI's definition: four or more killed, not including suspects, in an event. The killing may stretch over a day or more and some distance, especially if it includes killings committed in flight or against targeted people. It does not include an extended "cooling-off period" to distinguish this kind of crime from the acts of serial killers.
Unlike gun control advocates who just count shootings, USA TODAY analyzed all mass killings, regardless of weapon. That adds significant diversity to the types of killers and victims and produces a fuller portrait of this type of crime.
USA TODAY collected the FBI's Supplemental Homicide Reports from 2006 to 2014. This data, created by local police and collated by the FBI, provide details on each murder. However, Florida does not report to the FBI; the District of Columbia and Nebraska only started doing so in 2009; and murders on American Indian reservations, college campuses and military bases may not be included. To fill these gaps, USA TODAY used local news reports and official records. USA TODAY did the same for mass killings from 2015 to 2017, for which FBI data was not available.
USA TODAY cross-checked each FBI report with local news reports and sometimes with local law enforcement agencies. USA TODAY found some mass killings erroneously reported in the FBI data. In some cases, other types of crime were miscoded as murders. In other cases, miscodes created a mass killing where no crime had occurred. USA TODAY excluded these from its analysis.
USA TODAY also found mass killings not recorded in FBI data. Sometimes, a killer's victims, separated by a few miles or hours, were reported as separate cases. Example: An Alabama man killed his mother and torched her house. He drove 12 miles to his uncle's house, where he sprayed the front porch with gunfire, killing five and wounding one. Then he killed his grandmother, who lived next door, as she stood in a doorway. As he fled in a car, he shot eight more, three fatally, before killing himself.
USA TODAY did not include events if deaths stemmed from negligence, such as drunken driving, even if someone was convicted. Such cases involved crimes but showed no intent to commit a mass killing. Example: Two Pittsburgh women pleaded no contest to charges stemming from a house fire that broke out where they had left two 8-year-olds in charge of three younger children. All five died.
Weapons: USA TODAY counted just those a killer had “at hand” -- carried in the act. USA TODAY did not include weapons left in a vehicle or at home.
Relationships: For more than 1,000 victims, USA TODAY determined the relationship to the killer through news accounts and police and court documents. In some cases, it was impossible to tell how close a killer might have been to some types of victims, such as a family friend, co-worker or tenant. USA TODAY grouped relationships into four broad categories based on social and family distance.