SEATTLE >> Just seven months into 2019, the U.S. has experienced almost as many mass killings as occurred in all of 2018.

Back-to-back mass shootings in Texas and Ohio brought the total number of mass killings so far this year to 23, leaving 131 people dead. There were 25 mass killings in 2018, claiming 140 lives, according to a database compiled by The Associated Press, Northeastern University and USA Today.

The database tracks every mass killing dating back to 2006, and the El Paso and Dayton massacres had traits that were similar to many earlier incidents. That includes shooting a family member while carrying out a mass killing, which happened in Dayton; the young age of the perpetrators; and the tendency of the shooters to commit suicide or get killed by police.

Here are some takeaways:

OVERALL NUMBERS

The last three years have seen several fluctuations in mass killing numbers. In 2017, 225 people died in 32 mass killings, driven by the massacre in Las Vegas. In 2018, the year was marked by a surge in mass killings in public places, including schools in Texas and Florida.

A typical year has roughly 29 mass killings.

Mass killings — defined as killings involving four or more fatalities, not including the killer — have occurred in 16 states this year. California has experienced four of them.

FAMILY MEMBERS KILLED

The majority of mass killings involve domestic violence, and eight of 74 public mass shootings since 2006 involved the killing of a blood relative, the data shows. The shooter’s parent, sibling, cousin, nephew or niece was shot first and then the perpetrator sought out others to kill.

“They’ll take it out on family and then society, figuring they already committed a murder,” said David Chipman, a former agent with the Bureau of Alcohol, Tobacco, Firearms and Explosives who now works as a policy adviser at Giffords: Courage to Fight Gun Violence. “Domestic violence is the most risky call for service that police go on.”

Before 20-year-old Adam Lanza killed 26 children and staff at the Sandy Hook Elementary School in 2012, he had fatally shot his mother in their Newtown, Connecticut home.

Jaylen Fryberg, 15, sent text messages to lure two cousins and several friends to the cafeteria at Marysville Pilchuck High School in Marysville, Washington, in 2014. He then shot the four students before turning the gun on himself.

And last month, police say a man in Southern California began his rampage by killing and injuring family members before shooting strangers. In the end, he is accused of killing four people.

YOUNG KILLERS

The AP/USA Today/Northeastern database shows that many mass shootings are committed by a certain demographic: young, white men.

Most mass shootings in the U.S. are carried out by men, with white men making up nearly 50 percent of the shooters, the database shows.

The median age of a public mass shooter is 28; significantly lower than the median age of a person who commits a mass shooting of their family, according to the database.

Since 2006, 12 mass shootings have been committed by gunmen 21 or younger. That includes the 21-year-old suspected gunman in El Paso.

ARRESTED OR KILLED

More than half of public mass shooters either kill themselves on the scene or are shot by police.

Lanza and Fryberg killed themselves, as did Stephen Paddock, the man who killed 58 people and wounded 422 attending a country music festival in Las Vegas in 2017. So did the man who killed 33 at Virginia Tech in 2007; the former municipal worker who murdered 12 in Virginia Beach this year; and the mentally ill man who gunned down four at an IHop restaurant in Nevada in 2011. The Pulse nightclub shooter was killed by police in Orlando.

The man who opened fire at the Gilroy Garlic Festival in July also committed suicide.

“They obviously went through the thought process of ‘I may end up dead,’” said Frank Farley, a Temple University psychology professor and former president of the American Psychological Association. “And did it anyway.”

James Holmes, who killed 12 and wounded 70 in a movie theater in Aurora, Colorado, was sentenced in 2015 to life in prison. Dylann Roof, a white supremacist who fatally shot nine people attending the Emanuel African Methodist Episcopal Church in 2015, was sentenced to death.

Prosecutors are also seeking the death penalty for Patrick Wood Crusius, the man accused of fatally shooting 22 people at an El Paso Walmart.