GEOFF BENNETT: Good evening, and welcome to the "NewsHour."

As we come on the air, we are tracking developments in two major stories, Americans witnessing the horror of another mass shooting, a deadly assault on a school, and Israelis witnessing a day unlike any before it, an upheaval that paralyzed the country.

AMNA NAWAZ: First to the attack in Tennessee's capital city that left the shooter and six people dead, including three children at a church-run school.

The police chief said he was moved to tears by the tragedy.

Stephanie Sy begins our coverage.

STEPHANIE SY: In a scene that has become all too familiar in this country, first responders in Nashville, Tennessee, this morning rushed to respond to reports of an active school shooter, this time at the Covenant School, a private Christian elementary school of about 200 students.

Tennessee police initially set a female suspect entered the school and killed three children and three staff members, before being shot and killed by responding officers.

The children were identified as Evelyn Dieckhaus, Hallie Scruggs, and William Kinney, and the adult victims, all in their 60s, were named Cynthia Peak, Katherine Koonce, and Mike Hill.

The shooter was later identified as Audrey Hale, transgender, 28 years old and a former student at the school.

Don Aaron with the Nashville Police Department described the weapons used.

DON AARON, Public Information Officer, Nashville Police Department: We know that she was armed with at least two assault-type rifles and a handgun.

She entered the school through a side entrance and traversed her way from the first floor to the second floor, firing multiple shots.

STEPHANIE SY: Nashville police say it took less than 15 minutes from the first emergency call to when police officers stopped the shooter.

Nashville Police Chief John Drake described the goal of their response.

JOHN DRAKE, Metro Nashville Police Chief: I hoped that we would never have this situation, that, if we ever did, we would not wait, we would immediately go in and we would immediately engage the person perpetrating this horrible crime.

STEPHANIE SY: Shortly after the shooting, first responders escorted the surviving students from the Covenant School to buses, where they were reunited with their families, who were gathered at a nearby church.

Today, at the White House, President Biden called for more action.

JOE BIDEN, President of the United States: We have to do more to stop gun violence.

It's ripping our communities apart, ripping the soul of this nation, ripping at the very soul of the nation.

And we have to do more to protect our schools, so they aren't turned into prisons.

So, I call on Congress again to pass my assault weapons ban.

It's about time that we began to make some more progress.

STEPHANIE SY: Seventy-four people have either died or been wounded by shootings on K-12 campuses since the start of the year.

And, last year, 273 people were injured or killed in school shootings, the highest on record.

Last year, gun violence overtook car accidents as the leading cause of death for children in the United States.

Ashbey Beasley and her then 6-year-old son survived the Highland Park shooting in Chicago last Fourth of July, and happened to be in Nashville on a family vacation.

She attended the police briefing.

ASHBEY BEASLEY, Highland Park Shooting Survivor: I have met with over 130 lawmakers.

How is this still happening?

How are our children still dying?

And why are we failing them?

STEPHANIE SY: Those are questions that many Americans are asking as well.

For the "PBS NewsHour," I'm Stephanie Sy.

GEOFF BENNETT: Police also said that two of the three weapons used appeared to have been obtained legally.

To help us understand more about what transpired today, we turn to Jillian Peterson, the co-founder of The Violence Project.

That's a nonprofit dedicated to data-driven violence prevention.

She's also an associate professor of criminology and criminal justice at Hamline University in St. Paul, Minnesota.

Thank you for being with us.

The terror of gun violence once again visited upon what are supposed to be places of refuge, a school, a school on church grounds.

Jillian, what about this case stands out to you?

JILLIAN PETERSON, The Violence Project: You know, there's a number of things that actually stand out to me about this case, the first being that it was an elementary school -- those are rare -- and also a small, private elementary school.

We tend to see school mass shootings at large, typically suburban public high schools.

And so this is unique in terms of the location.

And what's coming out about the perpetrator, some of the facts seem unique as well.

The fact that the perpetrator identified as transgender is unique in our database, where we look at just K-12 school mass shooters who killed four or more people at school.

They are -- 100 percent identify as male.

GEOFF BENNETT: Police say the shooter was armed with two assault-type rifles and a handgun.

President Biden, as we saw in Stephanie's report today, is reviving his push for a federal assault ban, a federal assault rifle ban, in the aftermath of this tragedy.

How often are assault weapons used in mass shootings?

JILLIAN PETERSON: That number has been increasing, actually.

So the most common gun used is still a handgun.

When it comes to K-12 school shootings, shooters tend to use handguns, oftentimes because they are students of the school, and they're not old enough to purchase guns, so they're stealing guns from home from their parents or grandparents.

However, we have seen a real, marked increase in the number of perpetrators using those AR-15-style assault weapons.

Particularly in the past sort of three to four years, those numbers have just skyrocketed.

GEOFF BENNETT: There have been more than 100 mass shootings this year so far, a disturbing milestone that really highlights the uniquely American problem with gun violence.

School shootings are also on the rise.

You have led large-scale research studies on preventing gun violence.

What more needs to be done?

JILLIAN PETERSON: Yes, with our research, we coded about 200 perpetrators on nearly 200 different life history variables.

We talked to perpetrators.

We talked to people who knew them and tried to understand, what is that pathway to violence, and what does it look like?

And in our book called "The Violence Project," we identified over 30 different prevention strategies that we could be using, things like suicide prevention, because so many of these are suicides, crisis intervention teams, anonymous reporting systems, and then anything that makes it harder for somebody who is in a crisis, who is at risk of hurting themselves or someone else, anything we can do to make it harder for them to get their hands on a gun.

GEOFF BENNETT: Tennessee recently enacted a law allowing most people over the age of 21 to conceal-carry.

And Tennessee is not alone.

In fact, now half of America's 50 states now allow people to carry guns without first seeking a permit.

In your research, is there any connection between the passage of these kinds of laws and an increase in gun violence?

JILLIAN PETERSON: You know, that law in particular is actually very difficult to study.

And, in general, mass shootings, while they are happening with alarming frequency, they're still relatively rare events.

So it's hard to know when different laws get passed kind of what contributed and why, research-wise.

What we do know is that it is very easy for people who are in crisis, who are telling people that they are thinking about violence, who are wanting to die themselves, it is very easy for them to get their hands on a firearm legally in this country.

And we know that that is having a contributing effect.

GEOFF BENNETT: What will you be watching for as this investigation continues?

JILLIAN PETERSON: It's always -- there's always discussion of motive.

Perpetrators typically target something that represents their grievance with the world, that represents their anger.

Oftentimes, they want to get a message out to the world to show people their anger and to be known for doing this.

So, we will see if a manifesto comes out or more information emerges about motive.

And then it's always really important to look at, what were the warning signs leading up to this?

Did this person tell other people?

Did the perpetrator leak their plans?

Were they in a known crisis?

Is there something we can learn from the shooting that would allow us to prevent the next one?

GEOFF BENNETT: Jillian Peterson.

Jillian, thank you for your insights.

We appreciate it.

JILLIAN PETERSON: Thank you so much for having me.