Americans still reeling from mass shootings in Texas and Ohio can expect more carnage this year, according to research by Northwestern University.

The country will likely see between two and four more mass shooting events before the end of the year if current trends continue and no action is taken to combat the problem, said Lori Post, a sociologist and epidemiologist who studies mass shootings at the university’s Feinberg School of Medicine.

“We’re on a straight, upward trajectory,” Post said in an interview late last week.

Last year, the country experienced eight mass shooting events — the most in a single year since 1982 when Post’s dataset begins. Post said she uses the FBI’s original definition of a mass shooting as a single event in which four or more people are killed in a public place.

The country has recorded six events already with nearly five months left, according to Post’s accounting.

“That was the sad thing about my study. We’re putting together a database ... and I had to leave room for more massacres,” she said.

Post said her study is not complete, but she decided to release some of the data trends she’s discovered in light of this month’s mass shootings.

There have been 97 mass shootings since 1982, Post said. Her study, which used data from a Mother Jones magazine investigation, media stories and police reports to tally the shootings, shows they are trending upwards. There have only been three years during that time period with no mass shootings.

“We can see that it’s increasing at a really quick pace,” Post said. “But no actionable steps are ever taken.”

The study also found that 81% of mass shooters used semi-automatic, military-style weapons. Post said she attributes the steady increase in mass shootings to “more readily available” access to such weapons.

The characteristics of what make a rifle and “assault-style rifle” are still up for debate in the country, but Post said one thing is clear to her — the ability to fire a lot of bullets in a short period of time allows mass shooters the ability to kill and wound many people quickly.

“If you can make it to the emergency department, you’re more likely to live in 2019 than you were in 1982, so technology has increased on that side, but also gun lethality has increased as well,” she said.

Post also used her research to create a demographic profile of mass shooters, which found they are overwhelmingly committed by young, white males. She also identified additional risk factors, including a history of domestic violence incidents and protection orders, stalking and an inability to maintain relationships for an extended period of time.

Taken alone, none of the traits indicates someone’s potential for becoming a mass shooter, but Post said a background check program run at the federal level would allow authorities the ability to take the totality of traits into consideration, including when a person is stockpiling weapons and makes “hateful statements” in public forums.

“There’s a lot of concerning behaviors that lead up to these shootings,” Post said, citing reporting that the mother of the accused El Paso shooter had alerted police after her son bought a rifle. “We have to take notice.”

Post said the public and authorities need to pay more attention to people who make threats and to take them more seriously. Most mass shooters devote significant time to planning their attacks, she said.

Her research also showed few mass shooters are mentally ill, only making up less than 5% of shooters.

Post supports policies she believes would prevent more mass shootings, including red flag laws — which would permit law enforcement and courts to take the guns of a person deemed a danger to themselves or others. She also supports a ban on “high-capacity, rapid-fire” weapons and a limit on the number of bullets a gun’s magazine can hold.

On Friday, U.S. Senate Majority Leader Mitch McConnell, R-KY, said he has discussed background checks and red flag laws with President Trump and indicated the Senate could take up discussion of the issues when it reconvenes in the fall.